Image coding method, image decoding method, image coding apparatus, image decoding apparatus, and image coding and decoding apparatus

ABSTRACT

An image coding method includes: adding, to a candidate list, a first adjacent motion vector as a candidate for a predicted motion vector to be used for coding the current motion vector; selecting the predicted motion vector from the candidate list; and coding the current motion vector, wherein in the adding, the first adjacent motion vector indicating a position in a first reference picture included in a first reference picture list is added to the candidate list for the current motion vector indicating a position in a second reference picture included in a second reference picture list.

CROSS REFERENCE TO RELATED APPLICATION

The present application claims the benefit of U.S. Provisional PatentApplication No. 61/427,587 filed on Dec. 28, 2010. The entiredisclosures of the above-identified applications, including thespecifications, drawings and claims are incorporated herein by referencein their entirety.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates to an image coding method of coding animage with prediction, and an image decoding method of decoding an imagewith prediction.

(2) Description of the Related Art

An image coding apparatus generally compresses an information amountusing redundancy of images (including still images and moving images) inspatial and temporal directions. Here, transformation into a frequencydomain is used as the compression method using redundancy in the spatialdirection. Furthermore, inter prediction is used as the compressionmethod using redundancy in the temporal direction. The inter predictionis also called inter-picture prediction.

When coding a certain picture, the image coding apparatus that employsthe inter prediction uses, as a reference picture, a coded picturelocated before or after the current picture to be coded in displayorder. Subsequently, the image coding apparatus estimates a motionvector of the current picture with respect to the reference picture.

Next, the image coding apparatus obtains predicted image data resultingfrom motion compensation based on the motion vector. Then, the imagecoding apparatus obtains a difference between image data of the currentpicture and the predicted image data. Then, the image coding apparatuscodes the obtained difference. Accordingly, the image coding apparatusremoves the redundancy in the temporal direction.

The image coding apparatus in accordance with the moving picture codingscheme called H.264 (see Non-patent reference “ITU-T H.264 03/2010”)which has already been standardized uses three types of pictures, thatis, I-picture, P-picture, and B-picture to compress the informationamount. The image coding apparatus does not perform inter prediction onthe I-picture. In other words, the image coding apparatus performs intraprediction on the I-picture. The intra prediction is also calledintra-picture prediction.

Furthermore, the image coding apparatus performs inter prediction on theP-picture with reference to one coded picture located before or afterthe current picture in display order. Furthermore, the image codingapparatus performs inter prediction on the B-picture with reference totwo coded pictures located before or after the current picture indisplay order.

In the inter prediction, the image coding apparatus generates areference list (also called a reference picture list) for identifying areference picture. In the reference list, reference picture indexes areallocated to coded reference pictures to be referred to in the interprediction. For example, the image coding apparatus holds two referencelists (L0, L1) to refer to two pictures for the B-picture.

FIG. 33 illustrates an example of reference lists. The first referencepicture list (L0) of FIG. 33 is an example of a reference picture listcorresponding to a first prediction direction for the bi-directionalprediction. In the first reference picture list of FIG. 33, a referencepicture index indicated by 0 is allocated to a reference picture R1 in adisplay order 2. Furthermore, a reference picture index indicated by 1is allocated to a reference picture R2 in a display order 1.Furthermore, a reference picture index indicated by 2 is allocated to areference picture R3 in a display order 0.

In other words, in the first reference picture list of FIG. 33, asmaller reference picture index is allocated to a reference picture asthe reference picture is closer to the current picture in display order.

On the other hand, the second reference picture list (L1) of FIG. 33 isan example of a reference picture list corresponding to a secondprediction direction for the bi-directional prediction. In the secondreference picture list of FIG. 33, a reference picture index indicatedby 0 is allocated to the reference picture R2 in the display order 1.Furthermore, a reference picture index indicated by 1 is allocated tothe reference picture R1 in the display order 2. Furthermore, areference picture index indicated by 2 is allocated to the referencepicture R3 in the display order 0.

As such, there are cases where two different reference picture indexesare allocated to a particular reference picture (reference picture R1 orR2 in FIG. 33) included in the two reference picture lists. Furthermore,there are cases where the same reference picture index is allocated to aparticular reference picture (reference picture R3 in FIG. 33) includedin the two reference picture lists.

The prediction using only the first reference picture list (L0) iscalled the L0 prediction. The prediction using only the second referencepicture list (L1) is called the L1 prediction. The prediction using bothof the first reference picture list and the second reference picturelist is called the bi-directional prediction or bi-prediction.

In the L0 prediction, a forward direction is frequently used as aprediction direction. In the L1 prediction, a backward direction isfrequently used as a prediction direction. In other words, the firstreference picture list corresponds to the first prediction direction,and the second reference picture list corresponds to the secondprediction direction.

Based on these relationships, the prediction direction is categorizedinto one of the first prediction direction, the second predictiondirection, and the bi-direction. Furthermore, when the predictiondirection is the bi-direction, it may be also represented as thebi-directional prediction or bi-prediction.

The H.264 image coding scheme has a motion vector estimation mode as acoding mode for the block to be coded in the B-picture. In the motionvector estimation mode, the image coding apparatus estimates a motionvector for a block to be coded with reference to a reference picture.The image coding apparatus generates predicted image data using thereference picture and the motion vector. Then, the image codingapparatus codes (i) a difference between the predicted image data andimage data of the block to be coded and (ii) the motion vector to beused for generating the predicted image data.

The motion vector estimation mode may use the bi-directional predictionfor generating a predicted image with reference to two coded pictureslocated before or after the current picture. Furthermore, the motionvector estimation mode may use the one-directional prediction forgenerating a predicted image with reference to one coded picture locatedbefore or after the current picture. Then, one of the bi-directionalprediction and one-directional prediction is selected for a block to becoded.

When coding a motion vector in the motion vector estimation mode, theimage coding apparatus generates a predicted motion vector from a motionvector of a block, such as an adjacent coded block to the current block.The image coding apparatus codes a difference between the motion vectorand the predicted motion vector. Accordingly, the image coding apparatusreduces the information amount. The specific example will be describedwith reference to FIG. 34.

FIG. 34 illustrates a current block to be coded, an adjacent block A, anadjacent block B, and an adjacent block C. The adjacent block A is anadjacent coded block to the left of the current block. The adjacentblock B is an adjacent coded block above the current block. The adjacentblock C is an adjacent coded block to the upper right of the currentblock.

In FIG. 34, the adjacent block A has been coded with the bi-directionalprediction, and has a motion vector MvL0_A in the first predictiondirection, and a motion vector MvL1_A in the second predictiondirection. Here, the motion vector in the first prediction direction isa motion vector indicating a position in a reference picture identifiedby the first reference picture list. The motion vector in the secondprediction direction is a motion vector indicating a position in areference picture identified by the second reference picture list.

Furthermore, the adjacent block B has been coded with theone-directional prediction, and has a motion vector MvL0_B in the firstprediction direction. Furthermore, the adjacent block C has been codedwith the bi-directional prediction, and has a motion vector MvL0_C inthe first prediction direction, and a motion vector MvL1_C in the secondprediction direction. Furthermore, the current block is a block to becoded with the bi-directional prediction, and has a motion vector MvL0in the first prediction direction, and a motion vector MvL1 in thesecond prediction direction.

The image coding apparatus generates a predicted motion vector PMvL0corresponding to the first prediction direction, using an adjacent blockhaving a motion vector in the first prediction direction, when codingthe motion vector MvL0 in the first prediction direction of the currentblock. More specifically, the image coding apparatus generates thepredicted motion vector PMvL0 using the motion vector MvL0_A of theadjacent block A, the motion vector MvL0_B of the adjacent block B, andthe motion vector MvL0_C of the adjacent block C.

In other words, the image coding apparatus uses a motion vector in thefirst prediction direction of an adjacent block to the current block,when coding the motion vector MvL0 in the first prediction direction ofthe current block. Then, the image coding apparatus codes a differencebetween the motion vector MvL0 and the predicted motion vector PMvL0.

The predicted motion vector PMvL0 is calculated using Median (MvL0_A,MvL0_B, and MvL0_C) that is an equation for calculating a median value(central value) of the motion vectors MvL0_A, MvL0_B, and MvL0_C. Medianis represented by the following Equations 1 to 3.

[Math 1]

Median(x,y,z)=x+y+z−Min(x,Min(y,z))−Max(x,Max(y,z))  (Equation 1)

$\begin{matrix}\left\lbrack {{Math}\mspace{14mu} 2} \right\rbrack & \; \\{{{Min}\left( {x,y} \right)} = \left\{ \begin{matrix}x & \left( {x \leq y} \right) \\y & \left( {x > y} \right)\end{matrix} \right.} & \left( {{Equation}\mspace{14mu} 2} \right) \\\left\lbrack {{Math}\mspace{14mu} 3} \right\rbrack & \; \\{{{Max}\left( {x,y} \right)} = \left\{ \begin{matrix}x & \left( {x \geq y} \right) \\y & \left( {x < y} \right)\end{matrix} \right.} & \left( {{Equation}\mspace{14mu} 3} \right)\end{matrix}$

The image coding apparatus generates a predicted motion vector PMvL1corresponding to the second prediction direction, using an adjacentblock having a motion vector in the second prediction direction, whencoding the motion vector MvL1 in the second prediction direction for thecurrent block. More specifically, the image coding apparatus generatesthe predicted motion vector PMvL1 using the motion vector MvL1_A of theadjacent block A and the motion vector MvL1_C of the adjacent block C.

In other words, the image coding apparatus uses a motion vector in thesecond prediction direction of an adjacent block to the current block,when coding the motion vector MvL1 in the second prediction direction ofthe current block. Then, the image coding apparatus codes a differentialmotion vector that is a difference between the motion vector MvL1 andthe predicted motion vector PMvL1. The predicted motion vector PMvL1 iscalculated using Median (MvL1_A, 0, and MvL1_C) and others.

SUMMARY OF THE INVENTION

When the number of motion vectors in the same prediction direction isless, the number of motion vectors to be used for calculating apredicted motion vector is less. In such a case, the coding efficiencyof the motion vectors will not be improved.

In the conventional method of calculating a predicted motion vector, theimage coding apparatus uses only the motion vectors in the firstprediction direction of adjacent blocks, when calculating the predictedmotion vector PMvL0 in the first prediction direction of the currentblock as described above. Here, the image coding apparatus does not usethe motion vectors in the second prediction direction of the adjacentblocks.

Furthermore, the image coding apparatus uses only the motion vectors inthe second prediction direction of adjacent blocks, when calculating thepredicted motion vector PMvL1 in the second prediction direction of thecurrent block. Here, the image coding apparatus does not use the motionvectors in the first prediction direction of the adjacent blocks.

In other words, the motion vectors of adjacent blocks to be used forcalculating a predicted motion vector are limited in the conventionalmethod. Thus, the optimal motion vector is not derived, and the codingefficiency will not be improved.

Thus, the present invention has an object of providing an image codingmethod and an image decoding method for deriving a predicted motionvector suitable for improving the coding efficiency of a motion vector.

In order to solve the problems, an image coding method according to anaspect of the present invention is a method of coding a current pictureper block with prediction using one or both of a first reference picturelist and a second reference picture list, and includes: adding, to acandidate list, a first adjacent motion vector as a candidate for apredicted motion vector to be used for coding a current motion vector,the first adjacent motion vector being a motion vector of a blockadjacent to a current block included in the current picture, and thecurrent motion vector being a motion vector of the current block;selecting the predicted motion vector to be used for coding the currentmotion vector, from the candidate list including the first adjacentmotion vector; and coding the current motion vector using the selectedpredicted motion vector, wherein in the adding, the first adjacentmotion vector is added to the candidate list for the current motionvector, the first adjacent motion vector indicating a position in afirst reference picture included in the first reference picture list,and the current motion vector indicating a position in a secondreference picture included in the second reference picture list.

Accordingly, the adjacent motion vector corresponding to the firstreference picture list is added to the candidate list corresponding tothe second reference picture list. Accordingly, the number of theoptions of predicted motion vectors increases. Thus, it is possible toderive a predicted motion vector suitable for improving the codingefficiency of the current motion vector.

Furthermore, in the adding, a second adjacent motion vector may befurther added, the second adjacent motion vector being a motion vectorof the adjacent block and indicating a position in a third referencepicture included in the second reference picture list.

Accordingly, the adjacent motion vector corresponding to the secondreference picture list is added to the candidate list corresponding tothe second reference picture list. Accordingly, the number of theoptions of predicted, motion vectors increases. Thus, it is possible toderive a predicted motion vector suitable for improving the codingefficiency of the current motion vector.

Furthermore, in the adding: it may be determined whether or not thesecond reference picture is identical to the third reference picture;the second adjacent motion vector may be added to the candidate listwhen it is determined that the second reference picture is identical tothe third reference picture; it may be determined whether or not thesecond reference picture is identical to the first reference picture;and the first adjacent motion vector may be added to the candidate listwhen it is determined that the second reference picture is identical tothe first reference picture.

Accordingly, only when the reference picture corresponding to thecurrent motion vector is identical to the reference picturecorresponding to the adjacent motion vector, the adjacent motion vectoris added to the candidate list. Thus, only when the adjacent motionvector is appropriate as a candidate for a predicted motion vector, theadjacent motion vector is added to the candidate list. Thus, anappropriate predicted motion vector is derived.

Furthermore, in the adding: it may be determined whether or not thesecond reference picture is identical to the first reference picturewhen it is determined that the second reference picture is not identicalto the third reference picture; and the first adjacent motion vector maybe added to the candidate list when it is determined that the secondreference picture is not identical to the third reference picture andthat the second reference picture is identical to the first referencepicture.

Accordingly, when the current motion vector corresponds to the secondreference picture list, the adjacent motion vector corresponding to thesecond reference picture list is preferentially added to the candidatelist. Thus, a more appropriate adjacent motion vector is added to thecandidate list as a candidate for a predicted motion vector.

Furthermore, in the adding: it may be determined whether or not thesecond reference picture is identical to the third reference picture bydetermining whether or not a display order of the second referencepicture identified by the second reference picture list and a secondreference index is identical to a display order of the third referencepicture identified by the second reference picture list and a thirdreference index; and it may be determined whether or not the is secondreference picture is identical to the first reference picture bydetermining whether or not the display order of the second referencepicture identified by the second reference picture list and the secondreference index is identical to a display order of the first referencepicture identified by the first reference picture list and a firstreference index.

Accordingly, whether or not the reference picture identified by thefirst reference picture list is identical to the reference pictureidentified by the second reference picture list is appropriatelydetermined based on the display orders.

Furthermore, in the adding, a motion vector having a magnitude of 0 maybe added as the candidate for the predicted motion vector, when it isdetermined that the second reference picture is not identical to thethird reference picture and that the second reference picture is notidentical to the first reference picture.

Accordingly, decrease in the number of candidates is suppressed. Thus, astate where no candidate exists in the candidate list is avoided.

Furthermore, in the adding, a plurality of index values and a pluralityof candidates for the predicted motion vector may be added to thecandidate list so that the index values are in one-to-one correspondencewith the candidates for the predicted motion vector, in the selecting,an index value may be selected from the candidate list as the predictedmotion vector, and in the coding, the selected index value may be codedso that a code of the index value is longer as the index value islarger.

Accordingly, the selected predicted motion vector is appropriatelycoded. Thus, the coder and the decoder select the same predicted motionvector.

Furthermore, in the adding, the first adjacent motion vector of theadjacent block may be added to the candidate list, the adjacent blockbeing one of a left adjacent block, an above-adjacent block, and anupper right adjacent block with respect to the current block.

Accordingly, a plurality of adjacent motion vectors is added to thecandidate list as candidates for the predicted motion vector.Accordingly, the number of the options of predicted motion vectorsincreases.

Furthermore, an image decoding method according to an aspect of thepresent invention may be a method of decoding a current picture perblock with prediction using one or both of a first reference picturelist and a second reference picture list, and include: adding, to acandidate list, a first adjacent motion vector as a candidate for apredicted motion vector to be used for decoding a current motion vector,the first adjacent motion vector being a motion vector of a blockadjacent to a current block included in the current picture, and thecurrent motion vector being a motion vector of the current block;selecting the predicted motion vector to be used for decoding thecurrent motion vector, from the candidate list including the firstadjacent motion vector; and decoding the current motion vector using theselected predicted motion vector, wherein in the adding, the firstadjacent motion vector may be added to the candidate list for thecurrent motion vector, the first adjacent motion vector indicating aposition in a first reference picture included in the first referencepicture list, and the current motion vector indicating a position in asecond reference picture included in the second reference picture list.

Accordingly, the adjacent motion vector corresponding to the firstreference picture list is added to the candidate list corresponding tothe second reference picture list. Accordingly, the number of theoptions of predicted motion vectors increases. Thus, it is possible toderive a predicted motion vector suitable for improving the codingefficiency of the current motion vector.

Furthermore, in the adding, a second adjacent motion vector may befurther added, the second adjacent motion vector being a motion vectorof the adjacent block and Indicating a position in a third referencepicture included in the second reference picture list.

Accordingly, the adjacent motion vector corresponding to the secondreference picture list is added to the candidate list corresponding tothe second reference picture list. Accordingly, the number of theoptions of predicted motion vectors increases. Thus, it is possible toderive a predicted motion vector suitable for improving the codingefficiency of the current motion vector.

Furthermore, in the adding: it may be determined whether or not thesecond reference picture is identical to the third reference picture;the second adjacent motion vector may be added to the candidate listwhen it is determined that the second reference picture is identical tothe third reference picture; it may be determined whether or not thesecond reference picture is identical to the first reference picture;and the first adjacent motion vector may be added to the candidate listwhen it is determined that the second reference picture is identical tothe first reference picture.

Accordingly, only when the reference picture corresponding to thecurrent motion vector is identical to the reference picturecorresponding to the adjacent motion vector, the adjacent motion vectoris added to the candidate list. Thus, only when the adjacent motionvector is appropriate as a candidate for a predicted motion vector, theadjacent motion vector is added to the candidate list. Thus, anappropriate predicted motion vector is derived.

Furthermore, in the adding: it may be determined whether or not thesecond reference picture is identical to the first reference picturewhen it is determined that the second reference picture is not identicalto the third reference picture; and the first adjacent motion vector maybe added to the candidate list when it is determined that the secondreference picture is not identical to the third reference picture andthat the second reference picture is identical to the first referencepicture.

Accordingly, when the current motion vector corresponds to the secondreference picture list, the adjacent motion vector corresponding to thesecond reference picture list is preferentially added to the candidatelist. Thus, a more appropriate adjacent motion vector is added to thecandidate list as a candidate for a predicted motion vector.

Furthermore, in the adding: it may be determined whether or not thesecond reference picture is identical to the third reference picture bydetermining whether or not a display order of the second referencepicture identified by the second reference picture list and a secondreference index is identical to a display order of the third referencepicture identified by the second reference picture list and a thirdreference index; and it may be determined whether or not the secondreference picture is identical to the first reference picture bydetermining whether or not the display order of the second referencepicture identified by the second reference picture list and the secondreference index is identical to a display order of the first referencepicture identified by the first reference picture list and a firstreference index.

Accordingly, whether or not the reference picture identified by thefirst reference picture list is identical to the reference pictureidentified by the second reference picture list is appropriatelydetermined based on the display orders.

Furthermore, in the adding, a motion vector having a magnitude of 0 maybe added as the candidate for the predicted motion vector, when it isdetermined that the second reference picture is not identical to thethird reference picture and that the second reference picture is notidentical to the first reference picture.

Accordingly, decrease in the number of candidates is suppressed. Thus, astate where no candidate exists in the candidate list is avoided.

Furthermore, in the adding, a plurality of index values and a pluralityof candidates for the predicted motion vector may be added to thecandidate list so that the index values are in one-to-one correspondencewith the candidates for the predicted motion vector, in the decoding, anindex value may be decoded, the index value being coded so that a codeof the index value is longer as the index value is larger, and in theselecting, the predicted motion vector corresponding to the decodedindex value may be selected from the candidate list.

Accordingly, the selected predicted motion vector is appropriatelydecoded. Thus, the coder and the decoder select the same predictedmotion vector.

Furthermore, in the adding, the first adjacent motion vector of theadjacent block may be added to the candidate list, the adjacent blockbeing one of a left adjacent block, an above-adjacent block, and anupper right adjacent block with respect to the current block.

Accordingly, a plurality of adjacent motion vectors is added to thecandidate list as candidates for the predicted motion vector.Accordingly, the number of the options of predicted motion vectorsincreases.

Furthermore, an image coding apparatus according to an aspect of thepresent invention may be an image coding apparatus that codes a currentpicture per block with prediction using one or both of a first referencepicture list and a second reference picture list, and include: anaddition unit configured to add, to a candidate list, a first adjacentmotion vector as a candidate for a predicted motion vector to be usedfor coding a current motion vector, the first adjacent motion vectorbeing a motion vector of a block adjacent to a current block included inthe current picture, and the current motion vector being a motion vectorof the current block; a selecting unit configured to select thepredicted motion vector to be used for coding the current motion vector,from the candidate list including the first adjacent motion vector; anda coding unit configured to code the current motion vector using theselected predicted motion vector, wherein the addition unit may beconfigured to add the first adjacent motion vector to the candidate listfor the current motion vector, the first adjacent motion vectorindicating a position in a first reference picture included in the firstreference picture list, and the current motion vector indicating aposition in a second reference picture included in the second referencepicture list.

Accordingly, the image coding method is implemented as the image codingapparatus.

Furthermore, an image decoding apparatus according to an aspect of thepresent invention may be an image decoding apparatus that decodes acurrent picture per block with prediction using one or both of a firstreference picture list and a second reference picture list, and include:an addition unit configured to add, to a candidate list, a firstadjacent motion vector as a candidate for a predicted motion vector tobe used for decoding a current motion vector, the first adjacent motionvector being a motion vector of a block adjacent to a current blockincluded in the current picture, and the current motion vector being amotion vector of the current block; a selecting unit configured toselect the predicted motion vector to be used for decoding the currentmotion vector, from the candidate list including the first adjacentmotion vector; and a decoding unit configured to decode the currentmotion vector using the selected predicted motion vector, wherein theaddition unit may be configured to add the first adjacent motion vectorto the candidate list for the current motion vector, the first adjacentmotion vector indicating a position in a first reference pictureincluded in the first reference picture list, and the current motionvector indicating a position in a second reference picture included inthe second reference picture list.

Accordingly, the image decoding method is implemented as the imagedecoding apparatus.

Furthermore, an image coding and decoding apparatus according to anaspect of the present invention may be an image coding and decodingapparatus that codes a current picture per block and decodes a currentpicture per block, with prediction using one or both of a firstreference picture list and a second reference picture list, and include:an addition unit configured to add, to a candidate list, a firstadjacent motion vector as a candidate for a predicted motion vector tobe used for coding or decoding a current motion vector, the firstadjacent motion vector being a motion vector of a block adjacent to acurrent block to be processed and included in the current picture to becoded or decoded, and the current motion vector being a motion vector ofthe current block; a selecting unit configured to select the predictedmotion vector to be used for coding or decoding the current motionvector, from the candidate list including the first adjacent motionvector; a coding unit configured to code the current motion vector usingthe selected predicted motion vector; and a decoding unit configured todecode the current motion vector using the selected predicted motionvector, wherein the addition unit may be configured to add the firstadjacent motion vector to the candidate list for the current motionvector, the first adjacent motion vector indicating a position in afirst reference picture included in the first reference picture list,and the current motion vector indicating a position in a secondreference picture included in the second reference picture list.

Accordingly, the image coding and decoding apparatus implements both ofthe functions of the image coding apparatus and the image decodingapparatus.

According to the present invention, a predicted motion vector suitablefor improving the coding efficiency of a motion vector is derived.Accordingly, it is possible to improve the coding efficiency of themotion vector.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects, advantages and features of the invention willbecome apparent from the following description thereof taken inconjunction with the accompanying drawings that illustrate a specificembodiment of the present invention. In the Drawings:

FIG. 1 illustrates a configuration of an image coding apparatusaccording to Embodiment 1;

FIG. 2 illustrates a flowchart of operations performed by the imagecoding apparatus according to Embodiment 1;

FIG. 3 illustrates a flowchart of processes for determining a predictiondirection according to Embodiment 1;

FIG. 4 illustrates a flowchart of processes for calculating a candidatelist according to Embodiment 1;

FIG. 5 illustrates a flowchart of processes for determining an additionflag according to Embodiment 1;

FIG. 6A illustrates an example of a candidate list for the firstprediction direction according to Embodiment 1;

FIG. 6B illustrates an example of a candidate list for the secondprediction direction according to Embodiment 1;

FIG. 7 illustrates an example of codes of predicted motion vectorindexes according to Embodiment 1;

FIG. 8 illustrates processes for selecting a predicted motion vectoraccording to Embodiment 1;

FIG. 9 illustrates a configuration of an image decoding apparatusaccording to Embodiment 2;

FIG. 10 illustrates a flowchart of operations performed by the imagedecoding apparatus according to Embodiment 2;

FIG. 11A illustrates a configuration of an image coding apparatusaccording to Embodiment 3;

FIG. 11B illustrates a flowchart of operations performed by the imagecoding apparatus according to Embodiment 3;

FIG. 12A illustrates a configuration of an image decoding apparatusaccording to Embodiment 4;

FIG. 12B illustrates a flowchart of operations performed by the imagedecoding apparatus according to Embodiment 4;

FIG. 13 illustrates a configuration of an image coding and decodingapparatus according to Embodiment 5;

FIG. 14 illustrates an overall configuration of a content providingsystem for implementing content distribution services;

FIG. 15 illustrates an overall configuration of a digital broadcastingsystem;

FIG. 16 illustrates a block diagram illustrating an example of aconfiguration of a television;

FIG. 17 illustrates a block diagram illustrating an example of aconfiguration of an information reproducing/recording unit that readsand writes information from or on a recording medium that is an opticaldisc;

FIG. 18 illustrates an example of a configuration of a recording mediumthat is an optical disc;

FIG. 19A illustrates an example of a cellular phone;

FIG. 19B illustrates an example of a configuration of the cellularphone;

FIG. 20 illustrates a structure of multiplexed data;

FIG. 21 schematically illustrates how each of the streams is multiplexedin multiplexed data;

FIG. 22 illustrates how a video stream is stored in a stream of PESpackets in more detail;

FIG. 23 illustrates a structure of TS packets and source packets in themultiplexed data;

FIG. 24 illustrates a data structure of a PMT;

FIG. 25 illustrates an internal structure of multiplexed datainformation;

FIG. 26 illustrates an internal structure of stream attributeinformation;

FIG. 27 illustrates steps for identifying video data;

FIG. 28 illustrates a block diagram illustrating an example of aconfiguration of an integrated circuit for implementing the movingpicture coding method and the moving picture decoding method accordingto each of Embodiments;

FIG. 29 illustrates a configuration for switching between drivingfrequencies;

FIG. 30 illustrates steps for identifying video data and switchingbetween driving frequencies;

FIG. 31 illustrates an example of a look-up table in which the standardsof video data are associated with the driving frequencies;

FIG. 32A illustrates an example of a configuration for sharing a moduleof a signal processing unit;

FIG. 32B illustrates another example of a configuration for sharing amodule of a signal processing unit;

FIG. 33 illustrates an example of two reference picture lists; and

FIG. 34 illustrates an example of the current block to be coded and thethree adjacent blocks.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will be described with reference todrawings. Embodiments described hereinafter indicate favorable andspecific examples of the present invention. The values, shapes,materials, constituent elements, positions and connections of theconstituent elements, steps, and orders of the steps indicated inEmbodiments are examples, and do not limit the present invention. Thepresent invention are limited only according to Claims. Although theconstituent elements that are not described in independent Claims thatdescribe the most generic concept of the present invention are notnecessary to solve the problems of the present invention, they aredescribed as components of the favorable embodiments.

Furthermore, the first reference picture list corresponds to the L0prediction, and the second reference picture list corresponds to the L1prediction. Furthermore, the first reference picture list corresponds tothe first prediction direction, and the second reference picture listcorresponds to the second prediction direction. Conversely, the firstreference picture list may correspond to the L1 prediction, and thesecond reference picture list may correspond to the L0 prediction.Similarly, the first reference picture list may correspond to the secondprediction direction, and the second reference picture list maycorrespond to the first prediction direction.

Embodiment 1

FIG. 1 is a block diagram illustrating a configuration of an imagecoding apparatus according to Embodiment 1.

An image coding apparatus 100 in FIG. 1 includes an orthogonaltransformation unit 102, a quantization unit 103, an inversequantization unit 105, an inverse orthogonal transformation unit 106, ablock memory 108, a frame memory 109, an intra prediction unit 110, aninter prediction unit 111, an inter prediction control unit 114, apicture type determining unit 113, a reference picture list managingunit 115, an addition determining unit 116, a variable length codingunit 104, a subtracting unit 101, an addition unit 107, and a switchunit 112.

The orthogonal transformation unit 102 performs transformation onpredicted error data between predicted image data generated by a unit tobe described later and an input image sequence from an image domain to afrequency domain. The quantization unit 103 quantizes the predictederror data transformed into the frequency domain. The inversequantization unit 105 inversely quantizes the predicted error dataquantized by the quantization unit 103. The inverse orthogonaltransformation unit 106 performs transformation on the predicted errordata inversely quantized by the inverse quantization unit 105 from thefrequency domain to the image domain.

The block memory 108 is a memory for storing a decoded image generatedfrom the predicted image data and the predicted error data inverselyquantized by the inverse quantization unit 105 per block. The framememory 109 is a memory for storing the decoded image per frame.

The picture type determining unit 113 determines in which picture typean input picture sequence is coded, either I-picture, B-picture, orP-picture, and generates picture type information. The intra predictionunit 110 generates the predicted image data through intra prediction ofthe current block, using the decoded image stored per block in the blockmemory 108. The inter prediction unit 111 generates the predicted imagedata through inter prediction of the current block, using the decodedimage stored per frame in the frame memory 109.

The reference picture list managing unit 115 generates a reference listwith the display orders of reference picture indexes for allocating thereference picture indexes to coded reference pictures to be referred toin the inter prediction.

Although the reference picture list managing unit 115 manages thereference pictures by the reference picture indexes and the displayorders in Embodiment 1, it may manage the reference pictures by thereference picture indexes and the coding orders.

The addition determining unit 116 determines whether or not a candidatefor a predicted motion vector (candidate predicted motion vector) isadded with reference to the first and second reference picture listsgenerated by the reference picture list managing unit 115. Morespecifically, the addition determining unit 116 determines whether ornot a candidate predicted motion vector in the first predictiondirection is added to a candidate list for the second predictiondirection of the coded block, in a method to be described later. Then,the addition determining unit 116 sets an addition flag.

The inter prediction control unit 114 determines a predicted motionvector to be used for coding so as to code a motion vector using one ofthe candidate predicted motion vectors having the smallest error withthe motion vector derived from the motion estimation. Here, the error isa difference value between the candidate predicted motion vector and themotion vector derived from the motion estimation.

Furthermore, the inter prediction control unit 114 generates a predictedmotion vector index corresponding to the determined predicted motionvector, per block. The inter prediction control unit 114 transmits thepredicted motion vector index, the error information of the candidatepredicted motion vectors, and the reference picture indexes to thevariable length coding unit 104.

The variable length coding unit 104 variable-length-codes the quantizedprediction error data, an inter prediction direction flag, the referencepicture indexes, and the picture type information to generate abitstream.

FIG. 2 is the outline procedure of processes of the image coding methodaccording to Embodiment 1. The inter prediction control unit 114determines a prediction direction when the current block is coded in themotion vector estimation mode (S101). Next, the inter prediction controlunit 114 determines whether or not the prediction direction in themotion vector estimation mode is the bi-directional prediction (S102).

When the prediction direction is the bi-directional prediction (Yes atS102), the inter prediction control unit 114 calculates a candidatepredicted motion vector list for each of the first and second predictiondirections in a method to be described later (S103, S104).

Next, the addition determining unit 116 determines whether or not thecandidate predicted motion vector in the first prediction direction isadded to the candidate predicted motion vector list for the secondprediction direction (S105). When the addition determining unit 116determines that the candidate predicted motion vector in the firstprediction direction is added (Yes at S105), the inter predictioncontrol unit 114 adds the candidate predicted motion vector in the firstprediction direction to the candidate predicted motion vector list forthe second prediction direction (S106).

Next, the inter prediction control unit 114 selects the predicted motionvector in the first prediction direction from the candidate predictedmotion vector list for the first prediction direction, and the predictedmotion vector in the second prediction direction from the candidatepredicted motion vector list for the second prediction direction. Then,the variable length coding unit 104 codes the predicted motion vectorindexes corresponding to the selected predicted motion vectors, and addsthe indexes to a bitstream (S107).

When the prediction direction in the motion vector estimation mode isthe one-directional prediction (No at S102), the inter predictioncontrol unit 114 determines whether or not the prediction direction inthe motion vector estimation mode is the second prediction direction(S108).

When the prediction direction is the second prediction direction (Yes atS108), the inter prediction control unit 114 calculates a candidatepredicted motion vector in the second prediction direction (S109). Next,the addition determining unit 116 determines whether or not thecandidate predicted motion vector in the first prediction direction isadded to the candidate predicted motion vector list for the secondprediction direction (S110). When the addition determining unit 116determines that the candidate predicted motion vector in the firstprediction direction is added (Yes at S110), the inter predictioncontrol unit 114 adds the candidate predicted motion vector in the firstprediction direction to the candidate predicted motion vector list forthe second prediction direction (S111).

Next, the inter prediction control unit 114 selects the predicted motionvector in the second prediction direction from the candidate predictedmotion vector list for the second prediction direction. Then, thevariable length coding unit 104 codes a predicted motion vector indexcorresponding to the selected predicted motion vector, and adds thecoded index to a bitstream (S112).

When the prediction direction is not the second prediction direction (Noat S108), the inter prediction control unit 114 calculates a candidatepredicted motion vector in the first prediction direction (S113). Next,the inter prediction control unit 114 selects the predicted motionvector in the first prediction direction from the candidate predictedmotion vector list for the first prediction direction. Then, thevariable length coding unit 104 codes a predicted motion vector indexcorresponding to the selected predicted motion vector, and adds thecoded index to a bitstream (S114).

Finally, the variable length coding unit 104 codes a reference pictureindex and an inter prediction direction flag indicating a predictiondirection of the motion vector estimation mode, and adds the interprediction direction flag and the reference picture index to a bitstream(S115).

Next, a method of determining a prediction direction in the motionvector estimation mode (S101) in FIG. 2 will be described in detail withreference to a procedure of processes in FIG. 3. The inter predictioncontrol unit 114 performs motion estimation on the reference pictureidentified by the reference picture index in the first predictiondirection and the reference picture identified by the reference pictureindex in the second prediction direction. Then, the inter predictioncontrol unit 114 generates the first and second motion vectorscorresponding to the two reference pictures (S201).

Here, the inter prediction control unit 114 calculates difference valuesbetween the current block to be coded in a picture to be coded andblocks in each of the reference pictures in the motion estimation. Then,the inter prediction control unit 114 determines the block having thesmallest difference value as a reference block, among the blocks in thereference picture. Then, the inter prediction control unit 114calculates a motion vector with reference to a position of the currentblock and a position of the reference block.

Next, the inter prediction unit 111 generates a predicted image in thefirst prediction direction, using the calculated first motion vector.The inter prediction control unit 114 calculates Cost1 that is a costwhen the current block is coded using the predicted image by, forexample, an R-D optimization model represented by the following Equation4 (S202).

Cost=D+λ×R  (Equation 4)

In Equation 4, D denotes coding artifacts. More specifically, D is, forexample, a sum of absolute differences between (i) pixel values obtainedby coding and decoding the current block using the predicted imagegenerated from a certain motion vector and (ii) original pixel values ofthe current block. Furthermore, R denotes a generated code amount. Morespecifically, R is, for example, a necessary code amount for coding amotion vector used for generating a predicted image. Furthermore, λdenotes a Lagrange's method of undetermined multiplier.

Next, the inter prediction unit 111 generates a predicted image in thesecond prediction direction, using the calculated second motion vector.Then, the inter prediction control unit 114 calculates Cost2 fromEquation 4 (S203).

Next, the inter prediction unit 111 generates a bi-directional predictedimage using the calculated first and second motion vectors. Here, theinter prediction unit 111 generates the bi-directional predicted imageby averaging, per pixel, the predicted image obtained from the firstmotion vector and the predicted image obtained from the second motionvector. Then, the inter prediction control unit 114 calculates CostBifrom Equation 4 (S204).

Then, the inter prediction control unit 114 compares Cost1, Cost2, andCostBi (S205). When CostBi is the smallest (Yes at S205), the interprediction control unit 114 determines the bi-directional prediction asthe prediction direction of the motion vector estimation mode (S206).When CostBi is not the smallest (No at S205), the inter predictioncontrol unit 114 compares Cost1 and Cost2 (S207).

When Cost1 is smaller (Yes at S207), the inter prediction control unit114 determines the one-directional prediction in the first predictiondirection as the motion vector estimation mode (S208). When Cost1 is notsmaller (No at S207), the inter prediction control unit 114 determinesthe one-directional prediction in the second prediction direction as themotion vector estimation mode (S209).

Although the inter prediction unit 111 averages the images for each ofthe pixels when the bi-directional predicted image is generated inEmbodiment 1, it may calculate a weighted average of the images andothers.

Next, a method of calculating a candidate predicted motion vector listin FIGS. 2 (S103, S104, S109, and S113) will be described in detail withreference to a procedure of processes in FIG. 4. The inter predictioncontrol unit 114 determines an adjacent block A to the left of thecurrent block, an adjacent block B above the current block, and anadjacent block C to the upper right of the current block (S301).

For example, the inter prediction control unit 114 determines; as theadjacent block A, a block to which an adjacent pixel to the left of thepixel located in the top left corner of the current block belongs.Furthermore, the inter prediction control unit 114 determines, as theadjacent block B, a block to which an adjacent pixel above the pixellocated in the top left corner of the current block belongs.Furthermore, the inter prediction control unit 114 determines, as theadjacent block C, a block to which an adjacent pixel to the upper rightof the upper right corner of the current block belongs.

Next, the inter prediction control unit 114 determines whether or noteach of the adjacent blocks A, B, and C satisfies both of two conditions(S302). One of the conditions is that the adjacent block N (N is one ofA, B, and C) has a motion vector in a prediction direction identical tothat of the motion vector of the current block. The other is that areference picture of the adjacent block N is identical to that of thecurrent block.

When the adjacent block N satisfies the two conditions (Yes at S302),the inter prediction control unit 114 adds adjacent motion vectors ofthe adjacent block N to a candidate predicted motion vector list (S303).Furthermore, the inter prediction control unit 114 calculates a medianvalue (central value) of the motion vectors of the adjacent block, andadds the median value to the candidate predicted motion vector list(S304).

The inter prediction control unit 114 adds the motion vector of theadjacent block having the prediction direction identical to that of thecorresponding motion vector of the current block, to the candidatepredicted motion vector list. Then, the inter prediction control unit114 does not add a motion vector of the adjacent block having aprediction direction different from that of the motion vector of thecurrent block. However, the inter prediction control unit 114 may add amotion vector of the adjacent block having a prediction directiondifferent from that of the motion vector of the current block, to thecandidate predicted motion vector list by setting the motion vector tobe added to 0.

Next, a method of determining an addition flag in FIG. 2 (S105, S110)will be described.

There is a case where the reference picture indicated by the referenceindex of the first prediction direction of the adjacent block isidentical to the reference picture indicated by the reference index ofthe second prediction direction of the current block. Generally, themotion vector in the first prediction direction of the adjacent blocktends to have a value relatively close to the value of the motion vectorin the second prediction direction of the current block.

Thus, in such a case, the inter prediction control unit 114 adds themotion vector in the first prediction direction of the adjacent block asa candidate predicted motion vector in the second prediction directionof the current block. In other words, the inter prediction control unit114 adds the candidate predicted motion vector in the first predictiondirection of the current block as the candidate predicted motion vectorin the second prediction direction.

As such, the image coding apparatus 100 adds not only the motion vectorin the second prediction direction of the adjacent block but also themotion vector in the first prediction direction, as the candidatepredicted motion vectors in the second prediction direction of thecurrent block to perform efficient coding.

In Embodiment 1, not limited to this configuration, the inter predictioncontrol unit 114 adds the candidate predicted motion vector in the firstprediction direction of the current block as the candidate predictedmotion vector in the second prediction direction.

For example, there is a case where the reference picture in the secondprediction direction of the adjacent block is identical to the referencepicture in the first prediction direction of the current block. Thus, insuch a case, the inter prediction control unit 114 may add the motionvector in the second prediction direction of the adjacent block as acandidate predicted motion vector in the first prediction direction ofthe current block.

In other words, the inter prediction control unit 114 may add thecandidate predicted motion vector in the second prediction direction ofthe current block as the candidate predicted motion vector in the firstprediction direction. In this configuration, the image coding apparatus100 can efficiently code the motion vectors.

Furthermore, the variable length coding unit 104 may code the additionflag, and adds the flag to a bitstream. Accordingly, a decoder candetermine whether or not the candidate predicted motion vector in thefirst prediction direction should be added with reference to theaddition flag. Thus, the computing amount in decoding can be reduced.

Furthermore, the variable length coding unit 104 may add an additionflag per block. Accordingly, it is possible to perform the flexibleswitching. Furthermore, the variable length coding unit 104 may add anaddition flag per picture. Accordingly, it is possible to improve thecoding efficiency and reduce the computing amount of the decoder.

Next, a method of determining an addition flag will be described indetail with reference to FIG. 5.

The addition determining unit 116 obtains a reference picture index ofthe second prediction direction of the current block (S401).Furthermore, the inter prediction control unit 114 obtains referencepicture indexes of the first prediction direction of the adjacent blocksA, B, and C (S402).

Next, the addition determining unit 116 determines whether or not thereference picture indicated by the reference picture index of the secondprediction direction of the current block is identical to the referencepicture indicated by the reference picture index of the first predictiondirection of the adjacent block (S403). Here, the addition determiningunit 116 makes the determination using the first and second referencepicture lists.

For example, the addition determining unit 116 obtains, from the secondreference picture list, the display order of the reference pictureindicated by the reference picture index of the second predictiondirection of the current block. Furthermore, the addition determiningunit 116 obtains, from the first reference picture list, the displayorder of the reference picture indicated by the reference picture indexof the first prediction direction of the adjacent block. The additiondetermining unit 116 compares these two display orders. When determiningthat the orders are identical to each other, the addition determiningunit 116 determines that the two reference pictures are identical.

When the reference picture in the second prediction direction of thecurrent block is identical to the reference picture in the firstprediction direction of the adjacent block (Yes at S403), the additiondetermining unit 116 turns ON the addition flag (S404). When thereference picture in the second prediction direction of the currentblock is not identical to the reference picture in the first predictiondirection of the adjacent block (No at S403), the addition determiningunit 116 turns OFF the addition flag (S405).

In Embodiment 1, the addition determining unit 116 determines whether ornot the two reference pictures are identical to each other withreference to the display orders. However, the addition determining unit116 may determine whether or not the two reference pictures areidentical to each other with reference to the coding orders and others.Furthermore, the addition determining unit 116 may perform the processesin FIG. 5 only when a result of the determination in FIG. 4 is false (Noat S302).

When a result of the determination in FIG. 4 is true (Yes at S302), theinter prediction control unit 114 adds the motion vector in the secondprediction direction of the adjacent block as a candidate predictedmotion vector in the second prediction direction of the current block.Here, adding again the motion vector in the first prediction directionof the adjacent block as a candidate predicted motion vector in thesecond-prediction direction of the current block is redundant.

Thus, the addition determining unit 116 may perform the processes inFIG. 5 only when a result of the determination in FIG. 4 is false (No atS302). Accordingly, only when the motion vector in the second predictiondirection of the adjacent block is not the candidate predicted motionvector in the second prediction direction of the current block, theinter prediction control unit 114 can add the motion vector in the firstprediction direction of the adjacent block as a candidate predictedmotion vector in the second prediction direction of the current block.Accordingly, it is possible to improve the coding efficiency.

Next, an example of a candidate predicted motion vector list generatedwith the processes (S103 to S106) in FIG. 2 when the current block hasthe motion vector MvL0 in the first prediction direction and the motionvector MvL1 in the second prediction direction as illustrated in FIG. 34will be described with reference to FIGS. 6A and 6B.

The following relationship will be assumed in FIG. 34. In other words,the reference picture in the first prediction direction of the currentblock is identical to the reference picture in the first predictiondirection of each of the adjacent blocks A, B, and C. Furthermore, thereference picture in the second prediction direction of the currentblock, the reference picture in the second prediction direction of eachof the adjacent blocks A and C, and the reference picture in the firstprediction direction of the adjacent block B are identical to eachother.

In the candidate predicted motion vector list for the first predictiondirection of FIG. 6A, the predicted motion vector index corresponding toMedian (MvL0_A, MvL0_B, MvL0_C) is 0. The predicted motion vector indexcorresponding to the motion vector MvL0_A is 1. The predicted motionvector index corresponding to the motion vector MvL0_B is 2. Thepredicted motion vector index corresponding to the motion vector MvL0_Cis 3.

In the candidate predicted motion vector list for the second predictiondirection of FIG. 6B, the predicted motion vector index corresponding toMedian (MvL1_A, MvL0_B, MvL1_C) is 0. The predicted motion vector indexcorresponding to the motion vector MvL1_A is 1. The predicted motionvector index corresponding to the motion vector MvL0_B is 2. Thepredicted motion vector index corresponding to the motion vector MvL1_Cis 3.

Here, when the candidate predicted motion vector list for the secondprediction direction does not have a motion vector MvL1_B in the secondprediction direction of the adjacent block B, the inter predictioncontrol unit 114 adds the motion vector MvL0_B in the first predictiondirection to the candidate predicted motion vector list for the secondprediction direction. As such, when an adjacent block has no motionvector in the second prediction direction but instead has a motionvector in the first prediction direction, the inter prediction controlunit 114 adds the motion vector in the first prediction direction of theadjacent block to the candidate predicted motion vector list for thesecond prediction direction.

Accordingly, It is possible to improve the coding efficiency. When thecandidate predicted motion vector list for the second predictiondirection has no motion vector of the adjacent block, the interprediction control unit 114 does not allocate any predicted motionvector index. Accordingly, it is possible to improve the codingefficiency. Furthermore, the method of allocating the predicted motionvector index is not limited to this example. When no motion vector ispresent, the inter prediction control unit 114 may allocate thepredicted motion vector index by adding a motion vector having themagnitude of 0 to the candidate predicted motion vector list.

FIG. 7 illustrates an example of a code table for variable-length-codingpredicted motion vector indexes. As a predicted motion vector index issmaller, the code is shorter. The inter prediction control unit 114allocates a smaller predicted motion vector index to a candidateestimated with higher prediction precision. Accordingly, it is possibleto improve the coding efficiency.

In the example of the candidate predicted motion vector list for thesecond prediction direction in FIG. 6B, the inter prediction controlunit 114 allocates the predicted motion vector index indicated by 2, tothe motion vector MvL0_B in the first prediction direction of theadjacent block B. However, the inter prediction control unit 114 mayallocate a smaller predicted motion vector index to a candidate in thesame prediction direction.

More specifically, the inter prediction control unit 114 allocates 0 toa predicted motion vector index corresponding to Median (MvL1_A, MvL0_B,MvL1_C) in the candidate predicted motion vector list for the secondprediction direction.

Furthermore, the inter prediction control unit 114 allocates 1 to apredicted motion vector index corresponding to the motion vector MvL1_A.Furthermore, the inter prediction control unit 114 allocates 2 to apredicted motion vector index corresponding to the motion vector MvL1_C.Furthermore, the inter prediction control unit 114 allocates 3 to apredicted motion vector index corresponding to the motion vector MvL0_B.

Accordingly, the same prediction direction is prioritized, and thesmaller predicted motion vector Indexes are allocated to the candidatepredicted motion vectors estimated to have higher prediction precision.

Next, a method of selecting a predicted motion vector (S107, S112, andS114) of FIG. 2 will be described in detail with reference to aprocedure of processes in FIG. 8. The inter prediction control unit 114sets 0 to a counter value for initialization, and sets the largest valueto the smallest differential motion vector (S501).

Next, the inter prediction control unit 114 determines whether or notdifferential motion vectors of all the candidate predicted motionvectors are calculated (S502). When the candidate predicted motionvector still exists (Yes at S502), the inter prediction control unit 114calculates the differential motion vector by subtracting the candidatepredicted motion vector from a motion estimation result vector (S503).

Next, the inter prediction control unit 114 determines whether or notthe calculated differential motion vector is smaller than the smallestdifferential motion vector (S504). When the differential motion vectoris smaller than the smallest differential motion vector (Yes at S504),the inter prediction control unit 114 updates the smallest differentialmotion vector and the predicted motion vector index (S505).

Next, the inter prediction control unit 114 adds 1 to the counter value(S506). Then, the inter prediction control unit 114 determines againwhether or not the next candidate predicted motion vector exists (S502).When the inter prediction control unit 114 determines that thedifferential motion vectors for all the candidate predicted motionvectors are calculated (No at S502), it transmits the smallestdifferential motion vector and the predicted motion vector index thatare finally determined to the variable length coding unit 104, andcauses the variable length coding unit 104 to code the smallestdifferential motion vector and the predicted motion vector index (S507).

According to Embodiment 1, when selecting a motion vector of an adjacentblock as a candidate motion vector, the inter prediction control unit114 adopts a new selection criterion for the selection. Accordingly, theinter prediction control unit 114 derives a predicted motion vector themost suitable for coding a motion vector of the current picture.Accordingly, it is possible to improve the coding efficiency.

In particular, there is a case where the reference picture indicated bythe reference picture reference index of the second prediction directionof the current block is identical to the reference picture indicated bythe reference picture reference index of the first prediction directionof the adjacent block. In such a case, the inter prediction control unit114 adds the motion vector in the first prediction direction of theadjacent block as the candidate predicted motion vector in the secondprediction direction of the current block. Thus, the efficient coding ispossible.

In Embodiment 1, the inter prediction control unit 114 adds the motionvector in the first prediction direction of the adjacent block to thecandidate predicted motion vector list for the second predictiondirection of the current block. However, the inter prediction controlunit 114 may add the motion vector in the second prediction direction ofthe adjacent block to the candidate predicted motion vector list for thefirst prediction direction of the current block.

Embodiment 2

FIG. 9 is a block diagram illustrating a configuration of an imagedecoding apparatus according to Embodiment 2.

As illustrated in FIG. 9, an image decoding apparatus 200 includes avariable length decoding unit 204, an inverse quantization unit 205, aninverse orthogonal transformation unit 206, an addition unit 207, ablock memory 208, a frame memory 209, an intra prediction unit 210, aninter prediction unit 211, a switch unit 212, an inter predictioncontrol unit 214, a reference picture list managing unit 215, and anaddition determining unit 216.

The variable length decoding unit 204 variable-length-decodes an inputbitstream. Then, the variable length decoding unit 204 generates apicture type, a reference picture index, inter prediction directioninformation, a predicted motion vector index, and quantizedcoefficients. The inverse quantization unit 205 inversely quantizes thequantized coefficients. The inverse orthogonal transformation unit 206performs transformation on the inversely quantized orthogonaltransformation coefficients from the frequency domain to the imagedomain to generate prediction error image data.

The block memory 208 is a memory for storing an image sequence generatedby adding the predicted image data to the prediction error image data,per block. The frame memory 209 is a memory for storing the imagesequence per frame.

The intra prediction unit 210 generates the predicted image data of ablock to be decoded through intra prediction, using the image sequencestored per block in the block memory 208.

The inter prediction unit 211 generates the predicted image data of theblock to be decoded through inter prediction, using the image sequencestored per frame in the frame memory 209. The inter prediction controlunit 214 controls a method of generating a motion vector and predictedimage data in the inter prediction, according to the picture type, thereference picture index, the inter prediction direction information, andthe predicted motion vector index.

The reference picture list managing unit 215 generates a reference listwith the display orders of reference picture indexes for allocating thereference picture indexes to decoded reference pictures to be referredto in the inter prediction (similar to FIG. 33). The B-picture is usedfor coding with reference to two pictures. Thus, the reference picturelist managing unit 215 holds two reference lists.

The reference picture list managing unit 215 manages the referencepictures by the reference picture indexes and the display orders inEmbodiment 2. However, the reference picture list managing unit 215 maymanage the reference pictures by the reference picture indexes and thecoding orders (decoding orders).

The addition determining unit 216 determines whether or not a candidatepredicted motion vector in the first prediction direction is added to acandidate predicted motion vector list for the second predictiondirection of the block to be decoded with reference to the first andsecond reference picture lists generated by the reference picture listmanaging unit 215. Then, the addition determining unit 216 sets anaddition flag. Since the procedure for determining the addition flag isthe same as that in FIG. 5 according to Embodiment 1, the descriptionthereof is omitted.

Finally, the addition unit 207 adds the decoded prediction error imagedata to the predicted image data to generate a decoded image sequence.

FIG. 10 is an outline procedure of processes of an image decoding methodaccording to Embodiment 2. First, the inter prediction control unit 214determines whether or not a decoded prediction direction is abi-direction (S601).

When the decoded prediction direction is the bi-direction (Yes at S601),the inter prediction control unit 214 calculates candidate predictedmotion vector lists for the first and second prediction directions(S602, S603). FIG. 4 according to Embodiment 1 is used for calculatingthe candidate predicted motion vector lists. The inter predictioncontrol unit 214 decodes the reference picture indexes of the first andsecond prediction directions from a bitstream. The addition determiningunit 216 determines whether or not a candidate predicted motion vectorin the first prediction direction is added to the candidate predictedmotion vector list for the second prediction direction (S604).

When the addition flag is turned ON, (Yes at S604), the inter predictioncontrol unit 214 adds the candidate predicted motion vector in the firstprediction direction to the candidate predicted motion vector list forthe second prediction direction (S605). The addition flag indicatingwhether or not the candidate predicted motion vector in the firstprediction direction is added is set in the same manner as FIG. 5according to Embodiment 1.

The inter prediction control unit 214 selects the predicted motionvectors indicated by the predicted motion vector indexes of the firstand second prediction directions that are decoded from the bitstream,from the candidate predicted motion vector lists for the first andsecond prediction directions. The inter prediction control unit 214 addsdifferential motion vectors in the first and second predictiondirections that are decoded from the bitstream, to the predicted motionvectors in the first and second prediction directions.

Accordingly, the inter prediction control unit 214 decodes the motionvectors in the first and second prediction directions (S606).

When the decoded prediction direction is not the bi-direction (No atS601), that is, when the inter prediction direction is one direction,the inter prediction control unit 214 determines whether or not theprediction direction is the second prediction direction (S607).

When the prediction direction is the second prediction direction (Yes atS607), the inter prediction control unit 214 calculates a candidatepredicted motion vector in the second prediction direction (S608). Theaddition determining unit 216 determines whether or not a candidatepredicted motion vector in the first prediction direction is added tothe candidate predicted motion vector list for the second predictiondirection (S609).

When the addition flag is turned ON, (Yes at S609), the inter predictioncontrol unit 214 adds the candidate predicted motion vector in the firstprediction direction to the candidate predicted motion vector list forthe second prediction direction (S610).

The inter prediction control unit 214 selects the predicted motionvector indicated by the predicted motion vector index of the secondprediction direction that is decoded from the bitstream, from thecandidate predicted motion vector list for the second predictiondirection. The inter prediction control unit 214 adds the selectedpredicted motion vector to the differential motion vector in the secondprediction direction that is decoded from the bitstream, thus decodingthe motion vector in the second prediction direction (S611).

When the prediction direction is not the second prediction direction (Noat S607), that is, when the prediction direction is the first predictiondirection, the inter prediction control unit 214 calculates a candidatepredicted motion vector in the first prediction direction (S612).

The inter prediction control unit 214 selects the predicted motionvector indicated by the predicted motion vector index of the firstprediction direction that is decoded from the bitstream, from thecandidate predicted motion vector list for the first predictiondirection. Then, the inter prediction control unit 214 adds the selectedpredicted motion vector to the differential motion vector in the firstprediction direction that is decoded from the bitstream, thus decodingthe motion vector in the first prediction direction (S613).

According to Embodiment 2, when selecting a motion vector of an adjacentblock as a candidate motion vector, the inter prediction control unit214 adopts a new selection criterion for the selection. Accordingly, apredicted motion vector the most suitable for decoding a motion vectoris derived. Furthermore, the coding efficiency will be improved.

In particular, there is a case where the reference picture indicated bythe reference picture reference index of the second prediction directionof the current block to be decoded is identical to the reference pictureindicated by the reference picture reference index of the firstprediction direction of the adjacent block. In such a case, the interprediction control unit 214 adds the motion vector in the firstprediction direction of the adjacent block as a candidate predictedmotion vector in the second prediction direction of the current block tobe decoded. Accordingly, the coding efficiency will be improved.

The inter prediction control unit 214 according to Embodiment 2 adds themotion vector in the first prediction direction of the adjacent block tothe candidate predicted motion vector list for the second predictiondirection of the current block. However, the inter prediction controlunit 214 may add the motion vector in the second prediction direction ofthe adjacent block to the candidate predicted motion vector list for thefirst prediction direction of the current block.

Embodiment 3

Embodiment 3 supplementarily describes an image coding apparatusincluding the characteristic constituent elements of the image codingapparatus 100 according to Embodiment 1.

FIG. 11A illustrates a configuration of the image coding apparatusaccording to Embodiment 3. An image coding apparatus 300 in FIG. 11Aincludes an addition unit 301, a selecting unit 302, and a coding unit303. The addition unit 301 mainly corresponds to the additiondetermining unit 116 according to Embodiment 1. The selecting unit 302mainly corresponds to the inter prediction control unit 114 according toEmbodiment 1. The coding unit 303 mainly corresponds to the variablelength coding unit 104 according to Embodiment 1.

Then, the image coding apparatus 300 codes the current picture perblock. Here, the image coding apparatus 300 performs prediction usingone or both of the first and second reference picture lists. In otherwords, the image coding apparatus 300 performs prediction using one orboth of the reference picture indicated by the first reference picturelist and the reference picture indicated by the second reference picturelist.

FIG. 11B is a flowchart of operations performed by the image codingapparatus 300 in FIG. 11A. First, the addition unit 301 adds the firstadjacent motion vector to a candidate predicted motion vector list to beused for coding the current motion vector, as a candidate for apredicted motion vector (S701).

The first adjacent motion vector is a motion vector of an adjacent blockthat is adjacent to the current block to be coded included in thecurrent picture to be coded. Furthermore, the first adjacent motionvector indicates a position in a first reference picture included in thefirst reference picture list. The current motion vector is a motionvector of the current block. Furthermore, the current adjacent motionvector indicates a position in a second reference picture included inthe second reference picture list.

Next, the selecting unit 302 selects a predicted motion vector to beused for coding the current motion vector, from a candidate listincluding the first adjacent motion vector (S702). Next, the coding unit303 codes the current motion vector using the selected predicted motionvector (S703).

Accordingly, the adjacent motion vector corresponding to the firstreference picture list is added to the candidate list corresponding tothe second reference picture list. Accordingly, the number of theoptions of predicted motion vectors increases. Accordingly, it ispossible to derive a predicted motion vector suitable for improving thecoding efficiency of the current motion vector.

Furthermore, the addition unit 301 may add the second adjacent motionvector to the candidate list. The second adjacent motion vector is amotion vector of an adjacent block, and indicates a position in a thirdreference picture included in the second reference picture list.

Accordingly, the adjacent motion vector corresponding to the secondreference picture list is added to the candidate list corresponding tothe second reference picture list. Accordingly, the number of theoptions of predicted motion vectors increases. Accordingly, it ispossible to derive a predicted motion vector suitable for improving thecoding efficiency of the current motion vector.

Furthermore, the addition unit 301 may determine whether or not thesecond reference picture is identical to the third reference picture.When determining that the second reference picture is identical to thethird reference picture, the addition unit 301 may add the secondadjacent motion vector to the candidate list. Furthermore, the additionunit 301 may determine whether or not the second reference picture isidentical to the first reference picture. Then, when determining thatthe second reference picture is identical to the first referencepicture, the addition unit 301 may add the first adjacent motion vectorto the candidate list.

Accordingly, only when the reference picture corresponding to thecurrent motion vector is identical to the reference picturecorresponding to the adjacent motion vector, the adjacent motion vectoris added to the candidate list. Thus, only when the adjacent motionvector is appropriate as a candidate for a predicted motion vector, theadjacent motion vector is added to the candidate list. Thus, anappropriate predicted motion vector is derived.

Furthermore, the addition unit 301 may determine whether or not thesecond reference picture is identical to the first reference picturewhen determining that the second reference picture is not identical tothe third reference picture. When determining that the second referencepicture is not identical to the third reference picture and that thesecond reference picture is identical to the first reference picture,the addition unit 301 may add the first adjacent motion vector to thecandidate list.

Accordingly, when the current motion vector corresponds to the secondreference picture list, the adjacent motion vector corresponding to thesecond reference picture list is preferentially added to the candidatelist. Thus, a more appropriate adjacent motion vector is added to thecandidate list as a candidate for a predicted motion vector.

Furthermore, the addition unit 301 may determine whether or not thesecond reference picture is identical to the third reference picture bydetermining whether or not the display order of the second referencepicture is identical to the display order of the third referencepicture. Furthermore, the addition unit 301 may determine whether or notthe second reference picture is identical to the first reference pictureby determining whether or not the display order of the second referencepicture is identical to the display order of the first referencepicture.

Here, the first reference picture is identified by the first referencepicture list and the first reference index. Furthermore, the secondreference picture is identified by the second reference picture list andthe second reference index. Furthermore, the third reference picture isidentified by the second reference picture list and the third referenceindex.

Accordingly, whether or not the reference picture identified by is thefirst reference picture list is identical to the reference pictureidentified by the second reference picture list is appropriatelydetermined based on the display orders.

Furthermore, when determining that the second reference picture is notidentical to the third reference picture and that the second referencepicture is not identical to the first reference picture, the additionunit 301 may add 0 to the candidate list. In other words, the additionunit 301 may add a motion vector having a magnitude of 0 to thecandidate list as a candidate for a predicted motion vector.

Accordingly, decrease in the number of candidates is suppressed. Thus, astate where no candidate exists in the candidate list is avoided.

Furthermore, the addition unit 301 may add, to the candidate list, indexvalues and candidates for a predicted motion vector so that the indexvalues are in one-to-one correspondence with the candidates for thepredicted motion vector. Furthermore, the selecting unit 302 may selectan index value from the candidate list as a predicted motion vector. Thecoding unit 303 may further code the selected index value so that thecode of the index value is longer as the index value is larger.

Accordingly, the selected predicted motion vector is appropriatelycoded. Thus, the coder and the decoder select the same predicted motionvector.

Furthermore, the addition unit 301 may add the first adjacent motionvector of an adjacent block to the candidate list, assuming that each ofa left adjacent block, an above-adjacent block, and an upper rightadjacent block with respect to the current block to be coded is theadjacent block.

Accordingly, a plurality of adjacent motion vectors is added to thecandidate list as candidates for the predicted motion vector.Accordingly, the number of the options of predicted motion vectorsincreases.

Embodiment 4

Embodiment 4 supplementarily describes an image decoding apparatusincluding the characteristic constituent elements of the is imagedecoding apparatus 200 according to Embodiment 2.

FIG. 12A illustrates a configuration of the image decoding apparatusaccording to Embodiment 4. An image decoding apparatus 400 in FIG. 12Aincludes an addition unit 401, a selecting unit 402, and a decoding unit403. The addition unit 402 mainly corresponds to the additiondetermining unit 216 according to Embodiment 2. The selecting unit 402mainly corresponds to the inter prediction control unit 214 according toEmbodiment 2. The decoding unit 403 mainly corresponds to the variablelength decoding unit 204 and the Inter prediction control unit 214according to Embodiment 2.

The image decoding apparatus 400 decodes the current picture per block.Here, the image decoding apparatus 400 performs prediction using one orboth of the first and second reference picture lists. In other words,the image decoding apparatus 400 performs prediction using one or bothof the reference picture indicated by the first reference picture listand the reference picture indicated by the second reference picturelist.

FIG. 12B is a flowchart of operations performed by the image decodingapparatus 400 in FIG. 12A. First, the addition unit 401 adds the firstadjacent motion vector to a candidate predicted motion vector list to beused for decoding the current motion vector, as a candidate for apredicted motion vector (S801).

The first adjacent motion vector is a motion vector of an adjacent blockthat is adjacent to the current block to be decoded included in thecurrent picture to be decoded. Furthermore, the first adjacent motionvector indicates a position in a first reference picture included in thefirst reference picture list. The current motion vector is a motionvector of the current block to be decoded. Furthermore, the currentmotion vector indicates a position in a second reference pictureincluded in the second reference picture list.

Next, the selecting unit 402 selects a predicted motion vector to beused for decoding the current motion vector, from a candidate listincluding the first adjacent motion vector (S802). Next, the decodingunit 403 decodes the current motion vector using the selected predictedmotion vector (S803).

Accordingly, the adjacent motion vector corresponding to the firstreference picture list is added to the candidate list corresponding tothe second reference picture list. Furthermore, the number of theoptions of predicted motion vectors increases. Thus, it is possible toderive a predicted motion vector suitable for improving the codingefficiency of the current motion vector.

Furthermore, the addition unit 401 may add the second adjacent motionvector to the candidate list. The second adjacent motion vector is amotion vector of an adjacent block, and indicates a position in a thirdreference picture included in the second reference picture list.

Accordingly, the adjacent motion vector corresponding to the secondreference picture list is added to the candidate list corresponding tothe second reference picture list. Furthermore, the number of theoptions of predicted motion vectors increases. Thus, it is possible toderive a predicted motion vector suitable for improving the codingefficiency of the current motion vector.

Furthermore, the addition unit 401 may determine whether or not thesecond reference picture is identical to the third reference picture.Then, when determining that the second reference picture is identical tothe third reference picture, the addition unit 401 may add the secondadjacent motion vector to the candidate list. Furthermore, the additionunit 401 may determine whether or not the second reference picture isidentical to the first reference picture. Then, when determining thatthe second reference picture is identical to the first referencepicture, the addition unit 401 may add the first adjacent motion vectorto the candidate list.

Accordingly, only when the reference picture corresponding to thecurrent motion vector is identical to the reference picturecorresponding to the adjacent motion vector, the adjacent motion vectoris added to the candidate list. Thus, only when the adjacent motionvector is appropriate as a candidate for a predicted motion vector, theadjacent motion vector is added to the candidate list. Thus, anappropriate predicted motion vector is derived.

Furthermore, the addition unit 401 may determine whether or not thesecond reference picture is identical to the first reference picturewhen determining that the second reference picture is not identical tothe third reference picture. When determining that the second referencepicture is not identical to the third reference picture and that thesecond reference picture is identical to the first reference picture,the addition unit 401 may add the first adjacent motion vector to thecandidate list.

Accordingly, when the current motion vector corresponds to the secondreference picture list, the adjacent motion vector corresponding to thesecond reference picture list is preferentially added to the candidatelist. Thus, a more appropriate adjacent motion vector is added to thecandidate list as a candidate for a predicted motion vector.

Furthermore, the addition unit 401 may determine whether or not thesecond reference picture is identical to the third reference picture bydetermining whether or not the display order of the second referencepicture is identical to the display order of the third referencepicture. Furthermore, the addition unit 301 may determine whether or notthe second reference picture is identical to the first reference pictureby determining whether or not the display order of the second referencepicture is identical to the display order of the first referencepicture.

Here, the first reference picture is identified by the first referencepicture list and the first reference index. Furthermore, the secondreference picture is identified by the second reference picture list andthe second reference index. Furthermore, the third reference picture isidentified by the second reference picture list and the third referenceindex.

Accordingly, whether or not the reference picture identified by thefirst reference picture list is identical to the reference pictureidentified by the second reference picture list is appropriatelydetermined based on the display orders.

Furthermore, when determining that the second reference picture is notidentical to the third reference picture and that the second referencepicture is not identical to the first reference picture, the additionunit 401 may add 0 to the candidate list. In other words, the additionunit 401 may add a motion vector having a magnitude of 0 to thecandidate list as a candidate for a predicted motion vector.

Accordingly, decrease in the number of candidates is suppressed. Thus, astate where no candidate exists in the candidate list is avoided.

Furthermore, the addition unit 401 may add index values and candidatesfor a predicted motion vector to the candidate list so that the indexvalues are in one-to-one correspondence with the candidates for thepredicted motion vector. The decoding unit 403 may decode the indexvalue coded so that the code is longer as the index value is larger.Furthermore, the selecting unit 402 may select a predicted motion vectorcorresponding to the decoded index value, from the candidate list.

Accordingly, the selected predicted motion vector is appropriatelydecoded. Thus, the coder and the decoder select the same predictedmotion vector.

Furthermore, the addition unit 401 may add the first adjacent motionvector of the adjacent block to the candidate list, assuming that eachof a left adjacent block, an above-adjacent block, and an upper rightadjacent block with respect to the current block to be decoded is theadjacent block.

Accordingly, a plurality of adjacent motion vectors is added to thecandidate list as candidates for the predicted motion vector. Thus, thenumber of the options of predicted motion vectors increases.

Embodiment 5

Embodiment 5 supplementarily describes an image coding and decodingapparatus including the characteristic constituent elements of the imagecoding apparatus 100 according to Embodiment 1 and the image decodingapparatus 200 according to Embodiment 2.

FIG. 13 illustrates a configuration of the image coding and decodingapparatus according to Embodiment 5. An image coding and decodingapparatus 500 in FIG. 13 includes an addition unit 501, a selecting unit502, a coding unit 503, and a decoding unit 504.

The addition unit 501 mainly corresponds to the addition determiningunit 116 according to Embodiment 1 and the addition determining unit 216according to Embodiment 2. The selecting unit 402 mainly corresponds tothe inter prediction control unit 114 according to Embodiment 1 and theinter prediction control unit 214 according to Embodiment 2. The codingunit 503 mainly corresponds to the variable length coding unit 104according to Embodiment 1. The decoding unit 504 mainly corresponds tothe variable length decoding unit 204 and the inter prediction controlunit 214 according to Embodiment 2.

Then, the image coding and decoding apparatus 500 codes the currentpicture per block, and decodes the current picture per block. Here, theimage coding and decoding apparatus 500 performs prediction using one orboth of the first and second reference picture lists. In other words,the image coding and decoding apparatus 500 performs prediction usingone or both of the reference picture indicated by the first referencepicture list and the reference picture indicated by the second referencepicture list.

The addition unit 501 adds the first adjacent motion vector to acandidate predicted motion vector list to be used for coding or decodingthe current motion vector, as a candidate predicted motion vector.

The first adjacent motion vector is a motion vector of an adjacent blockthat is adjacent to a block to be processed included in the currentpicture to be coded or decoded. Furthermore, the first adjacent motionvector indicates a position in a first reference picture included in thefirst reference picture list. The current motion vector is a motionvector of the block to be processed. Furthermore, the current motionvector indicates a position in a second reference picture included inthe second reference picture list.

The selecting unit 502 selects a predicted motion vector to be used forcoding or decoding the current motion vector, from a candidate listincluding the first adjacent motion vector. The coding unit 503 codesthe current motion vector using the selected predicted motion vector.The decoding unit 504 decodes the current motion vector using theselected predicted motion vector.

Accordingly, the image coding and decoding apparatus 500 implements bothof the functions of the image coding apparatus and the image decodingapparatus.

Although the image coding apparatus and the image decoding apparatusaccording to the present invention are described based on Embodiments,the present invention is not limited to these Embodiments. The presentinvention includes modifications conceived by a person skilled in theart using Embodiments, and other embodiments arbitrarily combining theconstituent elements included In Embodiments.

For example, processes performed by a particular processing unit may beperformed by another processing unit. Furthermore, the order ofperforming the processes may be changed, and a plurality of processesmay be executed in parallel.

Furthermore, the present invention may be implemented not only as animage coding apparatus and an image decoding apparatus but also as amethod using, as steps, the processes performed by the processing unitsincluded in the image coding apparatus and the image decoding apparatus.For example, such steps are executed by a computer. Furthermore, thepresent invention can be implemented for causing a computer to executethe steps included in the method as a program. Furthermore, the presentinvention can be implemented as a computer-readable recording medium,such as a CD-ROM that records the program.

Accordingly, the image coding apparatus and the image decoding apparatusare implemented as an image coding and decoding apparatus by combiningthe constituent elements of the image coding apparatus and the imagedecoding apparatus.

Furthermore, each of the constituent elements included in the imagecoding apparatus and the image decoding apparatus may be implemented asa Large Scale Integration (LSI). The constituent elements may be madeinto one chip or a plurality of chips so as to include all or a part ofthe constituent elements. For example, the constituent elements otherthan a memory may be integrated into a single chip. The name used hereis LSI, but it may also be called IC, system LSI, super LSI, or ultraLSI depending on the degree of integration.

Moreover, ways to achieve integration are not limited to the LSI, and aspecial circuit or a general purpose processor and so forth can alsoachieve the integration. It is also acceptable to use a FieldProgrammable Gate Array (FPGA) that is programmable, and areconfigurable processor in which connections and settings of circuitcells within the LSI are reconfigurable.

In the future, with advancement in semiconductor technology, a brand-newtechnology may replace LSI. The constituent elements included in theimage coding apparatus and the image decoding apparatus can beintegrated into a circuit using such a technology.

Embodiment 6

The processing described in each of Embodiments can be simplyimplemented by recording, onto a recording medium, a program forimplementing the moving picture coding method (image coding method) orthe moving picture decoding method (image decoding method) described ineach of Embodiments. The recording medium may be any recording medium aslong as the program can be recorded thereon, such as a magnetic disk, anoptical disc, a magnetic optical disc, an IC card, and a semiconductormemory.

Hereinafter, the applications to the moving picture coding method (imagecoding method) and the moving picture decoding method (image decodingmethod) described in each of Embodiments and systems using thereof willbe described. The system is characterized by including an image codingand decoding apparatus including an image coding apparatus using animage coding method and an image decoding apparatus using an imagedecoding method. Other configuration in the system can be appropriatelychanged according to each individual case.

FIG. 14 illustrates an overall configuration of a content providingsystem ex100 for implementing content distribution services. The areafor providing communication services is divided into cells of desiredsize, and base stations ex106 to ex110 which are fixed wireless stationsare placed in each of the cells.

The content providing system ex100 is connected to devices, such as acomputer ex111, a personal digital assistant (PDA) ex112, a cameraex113, a cellular phone ex114 and a game machine ex115, via the Internetex101, an Internet service provider ex102, a telephone network ex104, aswell as the base stations ex106 to ex110.

However, the configuration of the content providing system ex100 is notlimited to the configuration shown in FIG. 14, and a combination inwhich any of the elements are connected is acceptable. In addition, eachof the devices may be directly connected to the telephone network ex104,rather than via the base stations ex106 to ex110 which are the fixedwireless stations. Furthermore, the devices may be interconnected toeach other via a short distance wireless communication and others.

The camera ex113, such as a digital video camera, is capable ofcapturing video. A camera ex116, such as a digital video camera, iscapable of capturing both still images and video. Furthermore, thecellular phone ex114 may be the one that meets any of the standards suchas Global System for Mobile Communications (GSM), Code Division MultipleAccess (CDMA), Wideband-Code Division Multiple Access (W-CDMA), LongTerm Evolution (LTE), and High Speed Packet Access (HSPA).Alternatively, the cellular phone ex114 may be a Personal HandyphoneSystem (PHS).

In the content providing system ex100, a streaming server ex103 isconnected to the camera ex113 and others via the telephone network ex104and the base station ex109, which enables distribution of a live showand others. For such a distribution, a content (for example, video of amusic live show) captured by the user using the camera ex113 is coded asdescribed above in each of Embodiments, and the coded content istransmitted to the streaming server ex103. On the other hand, thestreaming server ex103 carries out stream distribution of the receivedcontent data to the clients upon their requests. The clients include thecomputer ex111, the PDA ex112, the camera ex113, the cellular phoneex114, and the game machine ex115 that are capable of decoding theabove-mentioned coded data. Each of the devices that have received thedistributed data decodes and reproduces the coded data (that is,functions as an image decoding apparatus according to the presentinvention).

The captured data may be coded by the camera ex113 or the streamingserver ex103 that transmits the data, or the coding processes may beshared between the camera ex113 and the streaming server ex103.Similarly, the distributed data may be decoded by the clients or thestreaming server ex103, or the decoding processes may be shared betweenthe clients and the streaming server ex103. Furthermore, the data of thestill images and video captured by not only the camera ex113 but alsothe camera ex116 may be transmitted to the streaming server ex103through the computer ex111. The coding processes may be performed by thecamera ex116, the computer ex111, or the streaming server ex103, orshared among them.

Furthermore, the coding and decoding processes may be performed by anLSI ex500 generally included in each of the computer ex111 and thedevices. The LSI ex500 may be configured of a single chip or a pluralityof chips. Software for coding and decoding images may be integrated intosome type of a recording medium (such as a CD-ROM, a flexible disk, ahard disk) that is readable by the computer ex111 and others, and thecoding and decoding processes may be performed using the software.Furthermore, when the cellular phone ex114 is equipped with a camera,the moving picture data obtained by the camera may be transmitted. Thevideo data is data coded by the LSI ex500 included in the cellular phoneex114.

Furthermore, the streaming server ex103 may be composed of servers andcomputers, and may decentralize data and process the decentralized data,record, or distribute data.

As described above, the clients can receive and reproduce the coded datain the content providing system ex100. In other words, the clients canreceive and decode information transmitted by the user, and reproducethe decoded data in real time in the content providing system ex100, sothat the user who does not have any particular right and equipment canimplement personal broadcasting.

Aside from the example of the content providing system ex100, at leastone of the moving picture coding apparatus (image coding apparatus) andthe moving picture decoding apparatus (image decoding apparatus)described in each of Embodiments may be implemented in a digitalbroadcasting system ex200 illustrated in FIG. 15. More specifically, abroadcast station ex201 communicates or transmits, via radio waves to abroadcast satellite ex202, multiplexed data obtained by multiplexingaudio data and others onto video data. The video data is data coded bythe moving picture coding method described in each of Embodiments (thatis, data coded by the image coding apparatus according to the presentinvention). Upon receipt of the multiplexed data, the broadcastsatellite ex202 transmits radio waves for broadcasting. Then, a home-useantenna ex204 with a satellite broadcast reception function receives theradio waves. Next, a device such as a television (receiver) ex300 and aset top box (STB) ex217 decodes the received multiplexed data andreproduces the decoded data (that is, functions as the image decodingapparatus according to the present invention).

Furthermore, a reader/recorder ex218 that (i) reads and decodes themultiplexed data recorded on a recording media ex215, such as a DVD anda BD, or (ii) codes video signals in the recording medium ex215, and insome cases, writes data obtained by multiplexing an audio signal on thecoded data can include the moving picture decoding apparatus or themoving picture coding apparatus as shown in each of Embodiments. In thiscase, the reproduced video signals are displayed on the monitor ex219,and can be reproduced by another device or system using the recordingmedium ex215 on which the multiplexed data is recorded. Furthermore, itis also possible to implement the image decoding apparatus in the settop box ex217 connected to the cable ex203 for a cable television or theantenna ex204 for satellite and/or terrestrial broadcasting, so as todisplay the video signals on the monitor ex219 of the television ex300.The moving picture decoding apparatus may be included not in the set topbox but in the television ex300.

FIG. 16 illustrates the television (receiver) ex300 that uses the movingpicture coding method and the moving picture decoding method describedin each of Embodiments. The television ex300 includes: a tuner ex301that obtains or provides multiplexed data obtained by multiplexing audiodata onto video data, through the antenna ex204 or the cable ex203, etc.that receives a broadcast; a modulation/demodulation unit ex302 thatdemodulates the received multiplexed data or modulates data intomultiplexed data to be supplied outside; and amultiplexing/demultiplexing unit ex303 that demultiplexes the modulatedmultiplexed data into video data and audio data, or multiplexes videodata and audio data coded by a signal processing unit ex306 into data.

The television ex300 further includes: a signal processing unit ex306including an audio signal processing unit ex304 and a video signalprocessing unit ex305 (functioning as the image coding apparatus or theimage decoding apparatus according to the present invention) that decodeaudio data and video data and code audio data and video data,respectively; a speaker ex307 that provides the decoded audio signal;and an output unit ex309 including a display unit ex308 that displaysthe decoded video signal, such as a display. Furthermore, the televisionex300 includes an interface unit ex317 including an operation input unitex312 that receives an input of a user operation. Furthermore, thetelevision ex300 includes a control unit ex310 that controls overalleach constituent element of the television ex300, and a power supplycircuit unit ex311 that supplies power to each of the elements. Otherthan the operation input unit ex312, the interface unit ex317 mayinclude: a bridge ex313 that is connected to an external device, such asthe reader/recorder ex218; a slot unit ex314 for enabling attachment ofthe recording medium ex216, such as an SD card; a driver ex315 to beconnected to an external recording medium, such as a hard disk; and amodem ex316 to be connected to a telephone network. Here, the recordingmedium ex216 can electrically record information using anon-volatile/volatile semiconductor memory element for storage. Theconstituent elements of the television ex300 are connected to oneanother through a synchronous bus.

First, a configuration in which the television ex300 decodes dataobtained from outside through the antenna ex204 and others andreproduces the decoded data will be described. In the television ex300,upon a user operation from a remote controller ex220 and others, themultiplexing/demultiplexing unit ex303 demultiplexes the multiplexeddata demodulated by the modulation/demodulation unit ex302, undercontrol of the control unit ex310 including a CPU. Furthermore, theaudio signal processing unit ex304 decodes the demultiplexed audio data,and the video signal processing unit ex305 decodes the demultiplexedvideo data, using the decoding method described in each of Embodimentsin the television ex300. The output unit ex309 provides the decodedvideo signal and audio signal outside. When the output unit ex309provides the video signal and the audio signal, the signals may betemporarily stored in buffers ex318 and ex319, and others so that thesignals are reproduced in synchronization with each other. Furthermore,the television ex300 may read a coded bitstream not through a broadcastand others but from the recording media ex215 and ex216, such as amagnetic disk, an optical disc, and an SD card. Next, a configuration inwhich the television ex300 codes an audio signal and a video signal, andtransmits the data outside or writes the data on a recording medium willbe described. In the television ex300, upon a user operation from theremote controller ex220 and others, the audio signal processing unitex304 codes an audio signal, and the video signal processing unit ex305codes a video signal, under control of the control unit ex310 using thecoding method described in each of Embodiments. Themultiplexing/demultiplexing unit ex303 multiplexes the coded videosignal and audio signal, and provides the resulting signal outside. Whenthe multiplexing/demultiplexing unit ex303 multiplexes the video signaland the audio signal, the signals may be temporarily stored in buffersex320 and ex321, and others so that the signals are reproduced insynchronization with each other. Here, the buffers ex318, ex319, ex320,and ex321 may be plural as illustrated, or at least one buffer may beshared in the television ex300. Furthermore, data may be stored in abuffer other than the buffers ex318 to ex321 so that the system overflowand underflow may be avoided between the modulation/demodulation unitex302 and the multiplexing/demultiplexing unit ex303, for example.

Furthermore, the television ex300 may include a configuration forreceiving an AV input from a microphone or a camera other than theconfiguration for obtaining audio and video data from a broadcast or arecording medium, and may code the obtained data. Although thetelevision ex300 can code, multiplex, and provide outside data in thedescription, it may be not capable of performing all the processes butcapable of only one of receiving, decoding, and providing outside data.

Furthermore, when the reader/recorder ex218 reads or writes multiplexeddata from or on a recording medium, one of the television ex300 and thereader/recorder ex218 may decode or code the multiplexed data, and thetelevision ex300 and the reader/recorder ex218 may share the decoding orcoding.

As an example, FIG. 17 illustrates a configuration of an informationreproducing/recording unit ex400 when data is read or written from or inan optical disc. The information reproducing/recording unit ex400includes constituent elements ex401, ex402, ex403, ex404, ex405, ex406,and ex407 to be described hereinafter. The optical head ex401 irradiatesa laser spot on a recording surface of the recording medium ex215 thatis an optical disc to write information, and detects reflected lightfrom the recording surface of the recording medium ex215 to read theinformation. The modulation recording unit ex402 electrically drives asemiconductor laser included in the optical head ex401, and modulatesthe laser light according to recorded data. The reproductiondemodulating unit ex403 amplifies a reproduction signal obtained byelectrically detecting the reflected light from the recording surfaceusing a photo detector included in the optical head ex401, anddemodulates the reproduction signal by separating a signal componentrecorded on the recording medium ex215 to reproduce the necessaryinformation. The buffer ex404 temporarily holds the information to berecorded on the recording medium ex215 and the information reproducedfrom the recording medium ex215. A disk motor ex405 rotates therecording medium ex215. A servo control unit ex406 moves the opticalhead ex401 to a predetermined information track while controlling therotation drive of the disk motor ex405 so as to follow the laser spot.The system control unit ex407 controls overall the informationreproducing/recording unit ex400. The reading and writing processes canbe implemented by the system control unit ex407 using variousinformation stored in the buffer ex404 and generating and adding newinformation as necessary, and by the modulation recording unit ex402,the reproduction demodulating unit ex403, and the servo control unitex406 that record and reproduce information through the optical headex401 while being operated in a coordinated manner. The system controlunit ex407 includes, for example, a microprocessor, and executesprocessing by causing a computer to execute a program for read andwrite.

Although the optical head ex401 irradiates a laser spot in thedescription, it may perform high-density recording using near fieldlight.

FIG. 18 schematically illustrates the recording medium ex215 that is theoptical disc. On the recording surface of the recording medium ex215,guide grooves are spirally formed, and an information track ex230records, in advance, address information indicating an absolute positionon the disk according to change in a shape of the guide grooves. Theaddress information includes information for determining positions ofrecording blocks ex231 that are a unit for recording data. An apparatusthat records and reproduces data reproduces the information track ex230and reads the address information so as to determine the positions ofthe recording blocks. Furthermore, the recording medium ex215 includes adata recording area ex233, an inner circumference area ex232, and anouter circumference area ex234. The data recording area ex233 is an areafor use in recording the user data. The inner circumference area ex232and the outer circumference area ex234 that are inside and outside ofthe data recording area ex233, respectively are for specific use exceptfor recording the user data. The information reproducing/recording unitex400 reads and writes coded audio data, coded video data, or coded dataobtained by multiplexing the coded audio data and the coded video data,from and on the data recording area ex233 of the recording medium ex215.

Although an optical disc having a layer, such as a DVD and a BD isdescribed as an example in the description, the optical disc is notlimited to such, and may be an optical disc having a multilayerstructure and capable of being recorded on a part other than thesurface. Furthermore, the optical disc may have a structure formultidimensional recording/reproduction, such as recording of,information using light of colors with different wavelengths in the sameportion of the optical disc and recording information having differentlayers from various angles.

Furthermore, a car ex210 having an antenna ex205 can receive data fromthe satellite ex202 and others, and reproduce video on a display devicesuch as a car navigation system ex211 set in the car ex210, in thedigital broadcasting system ex200. Here, a configuration of the carnavigation system ex211 will be the one for example, including a GPSreceiving unit in the configuration illustrated in FIG. 16. The samewill be true for the configuration of the computer ex111, the cellularphone ex114, and others.

FIG. 19A illustrates the cellular phone ex114 that uses the movingpicture coding method and the moving picture decoding method describedin Embodiments. The cellular phone ex114 includes: an antenna ex350 fortransmitting and receiving radio waves through the base station ex110; acamera unit ex365 capable of capturing moving and still images; and adisplay unit ex358 such as a liquid crystal display for displaying thedata such as decoded video captured by the camera unit ex365 or receivedby the antenna ex350. The cellular phone ex114 further includes: a mainbody unit including a set of operation keys ex366; an audio output unitex357 such as a speaker for output of audio; an audio input unit ex356such as a microphone for input of audio; a memory unit ex367 for storingcaptured video or still pictures, recorded audio, coded or decoded dataof the received video, the still pictures, e-mails, or others; and aslot unit ex364 that is an interface unit for a recording medium thatstores data in the same manner as the memory unit ex367.

Next, an example of a configuration of the cellular phone ex114 will bedescribed with reference to FIG. 19B. In the cellular phone ex114, amain control unit ex360 designed to control overall each unit of themain body including the display unit ex358 as well as the operation keysex366 is connected mutually, via a synchronous bus ex370, to a powersupply circuit unit ex361, an operation input control unit ex362, avideo signal processing unit ex355, a camera interface unit ex363, aliquid crystal display (LCD) control unit ex359, amodulation/demodulation unit ex352, a multiplexing/demultiplexing unitex353, an audio signal processing unit ex354, the slot unit ex364, andthe memory unit ex367.

When a call-end key and a power key are turned ON by a user's operation,the power supply circuit unit ex360 supplies the respective units withpower from a battery pack so as to activate the cell phone ex114 that isdigital and is equipped with the camera.

In the cellular phone ex114, the audio signal processing unit ex354converts the audio signals collected by the audio input unit ex356 invoice conversation mode into digital audio signals under the control ofthe main control unit ex360 including a CPU, ROM, and RAM. Then, themodulation/demodulation unit ex352 performs spread spectrum processingon the digital audio signals, and the transmitting and receiving unitex351 performs digital-to-analog conversion and frequency conversion onthe data, so as to transmit the resulting data via the antenna ex350.Also, in the cellular phone ex114, the transmitting and receiving unitex351 amplifies the data received by the antenna ex350 in voiceconversation mode and performs frequency conversion and theanalog-to-digital conversion on the data. Then, themodulation/demodulation unit ex352 performs inverse spread spectrumprocessing on the data, and the audio signal processing unit ex354converts it into analog audio signals, so as to output them via theaudio output unit ex356.

Furthermore, when an e-mail in data communication mode is transmitted,text data of the e-mail inputted by operating the operation keys ex366and others of the main body is sent out to the main control unit ex360via the operation input control unit ex362. Then, themodulation/demodulation unit ex352 performs spread spectrum processingon the digital audio signals, and the transmitting and receiving unitex351 performs digital-to-analog conversion and frequency conversion onthe data, so as to transmit the resulting data via the antenna ex350.When an e-mail is received, processing that is approximately inverse tothe processing for transmitting an e-mail is performed on the receiveddata, and the resulting data is provided to the display unit ex358.

When video, still images, or video and audio in data communication modeis or are transmitted, the video signal processing unit ex355 compressesand codes video signals supplied from the camera unit ex365 using themoving picture coding method shown in each of Embodiments (that is,functioning as the image coding apparatus according to the presentinvention), and transmits the coded video data to themultiplexing/demultiplexing unit ex353. In contrast, during when thecamera unit ex365 captures video, still images, and others, the audiosignal processing unit ex354 codes audio signals collected by the audioinput unit ex356, and transmits the coded audio data to themultiplexing/demultiplexing unit ex353.

The multiplexing/demultiplexing unit ex353 multiplexes the coded videodata supplied from the video signal processing unit ex355 and the codedaudio data supplied from the audio signal processing unit ex354, using apredetermined method. Then, the modulation/demodulation unit(modulation/demodulation circuit unit) ex352 performs spread spectrumprocessing on the digital audio signals, and the transmitting andreceiving unit ex351 performs digital-to-analog conversion and frequencyconversion on the data, so as to transmit the resulting data via theantenna ex350.

When receiving data of a video file which is linked to a Web page andothers in data communication mode or when receiving an e-mail with videoand/or audio attached, in order to decode the multiplexed data receivedvia the antenna ex350, the multiplexing/demultiplexing unit ex353demultiplexes the multiplexed data into a video data bitstream and anaudio data bitstream, and supplies the video signal processing unitex355 with the coded video data and the audio signal processing unitex354 with the coded audio data, through the synchronous bus ex370. Thevideo signal processing unit ex355 decodes the video signal using amoving picture decoding method corresponding to the moving picturecoding method shown in each of Embodiments (that is, functioning as theimage decoding apparatus according to the present invention), and thenthe display unit ex358 displays, for instance, the video and stillimages included in the video file linked to the Web page via the LCDcontrol unit ex359. Furthermore, the audio signal processing unit ex354decodes the audio signal, and the audio output unit ex357 provides theaudio.

Furthermore, similarly to the television ex300, a terminal such as thecellular phone ex114 may have 3 types of implementation configurationsincluding not only (i) a transmitting and receiving terminal includingboth a coding apparatus and a decoding apparatus, but also (ii) atransmitting terminal including only a coding apparatus and (iii) areceiving terminal including only a decoding apparatus. Although thedigital broadcasting system ex200 receives and transmits the multiplexeddata obtained by multiplexing audio data onto video data in thedescription, the multiplexed data may be data obtained by multiplexingnot audio data but character data related to video onto video data, andmay be not multiplexed data but video data itself.

As such, the moving picture coding method and the moving picturedecoding method in each of Embodiments can be used in any of the devicesand systems described. Thus, the advantages described in each ofEmbodiments can be obtained.

Furthermore, the present invention is not limited to Embodiments, andvarious modifications and revisions are possible without departing fromthe scope of the present invention.

Embodiment 7

Video data can be generated by switching, as necessary, between (i) themoving picture coding method or the moving picture coding apparatusshown in each of Embodiments and (ii) a moving picture coding method ora moving picture coding apparatus in conformity with a differentstandard, such as MPEG-2, MPEG-4 AVC, and VC-1.

Here, when a plurality of video data that conforms to the differentstandards is generated and is then decoded, the decoding methods need tobe selected to conform to the different standards. However, since towhich standard each of the plurality of the video data to be decodedconforms cannot be identified, there is a problem that an appropriatedecoding method cannot be selected.

In order to solve the problem, multiplexed data obtained by multiplexingaudio data and others onto video data has a structure includingidentification information indicating to which standard the video dataconforms. The specific structure of the multiplexed data including thevideo data generated in the moving picture coding method and by themoving picture coding apparatus shown in each of Embodiments will behereinafter described. The multiplexed data is a digital stream in theMPEG2-Transport Stream format.

FIG. 20 illustrates a structure of the multiplexed data. As illustratedin FIG. 20, the multiplexed data can be obtained by multiplexing atleast one of a video stream, an audio stream, a presentation graphicsstream (PG), and an interactive graphics stream. The video streamrepresents primary video and secondary video of a movie, the audiostream (IG) represents a primary audio part and a secondary audio partto be mixed with the primary audio part, and the presentation graphicsstream represents subtitles of a movie. Here, the primary video isnormal video to be displayed on a screen, and the secondary video isvideo to be displayed on a smaller window in the main video.Furthermore, the interactive graphics stream represents an interactivescreen to be generated by arranging the GUI components on a screen. Thevideo stream is coded in the moving picture coding method or by themoving picture coding apparatus shown in each of Embodiments, or in amoving picture coding method or by a moving picture coding apparatus inconformity with a conventional standard, such as MPEG-2, MPEG-4 AVC, andVC-1. The audio stream is coded in accordance with a standard, such asDolby-AC-3, Dolby Digital Plus, MLP, DTS, DTS-HD, and linear PCM.

Each stream included in the multiplexed data is identified by PID. Forexample, 0x1011 is allocated to the video stream to be used for video ofa movie, 0x1100 to 0x111F are allocated to the audio streams, 0x1200 to0x121F are allocated to the presentation graphics streams, 0x1400 to0x141F are allocated to the interactive graphics streams, 0x1B00 to0x1B1F are allocated to the video streams to be used for secondary videoof the movie, and 0x1A00 to 0x1A1F are allocated to the audio streams tobe used for the secondary video to be mixed with the primary audio.

FIG. 21 schematically illustrates how data is multiplexed. First, avideo stream ex235 composed of video frames and an audio stream ex238composed of audio frames are transformed into a stream of PES packetsex236 and a stream of PES packets ex239, and further into TS packetsex237 and TS packets ex240, respectively. Similarly, data of apresentation graphics stream ex241 and data of an interactive graphicsstream ex244 are transformed into a stream of PES packets ex242 and astream of PES packets ex245, and further into TS packets ex243 and TSpackets ex246, respectively. These, TS packets are multiplexed into astream to obtain multiplexed data ex247.

FIG. 22 illustrates how a video stream is stored in a stream of PESpackets in more detail. The first bar in FIG. 22 shows a video framestream in a video stream. The second bar shows the stream of PESpackets. As indicated by arrows denoted as yy2, yy2, yy3, and yy4 inFIG. 22, the video stream is divided into pictures as I-pictures,B-pictures, and P-pictures each of which is a video presentation unit,and the pictures are stored in a payload of each of the PES packets.

Each of the PES packets has a PES header, and the PES header stores aPresentation Time-Stamp (PTS) indicating a display time of the picture,and a Decoding Time-Stamp (DTS) indicating a decoding time of thepicture.

FIG. 23 illustrates a format of TS packets to be finally written on themultiplexed data. Each of the TS packets is a 188-byte fixed lengthpacket including a 4-byte TS header having information, such as a PIDfor identifying a stream and a 184-byte TS payload for storing data. ThePES packets are divided, and stored in the TS payloads, respectively.When a BD ROM is used, each of the TS packets is given a 4-byteTP_Extra_Header, thus resulting in 192-byte source packets. The sourcepackets are written on the multiplexed data. The TP_Extra_Header storesinformation such as an Arrival_Time_Stamp (ATS). The ATS shows atransfer start time at which each of the TS packets is to be transferredto a PID filter. The numbers incrementing from the head of themultiplexed data are called source packet numbers (SPNs).

Each of the TS packets included in the multiplexed data includes notonly streams of audio, video, subtitles and others, but also a ProgramAssociation Table (PAT), a Program Map Table (PMT), and a Program ClockReference (PCR). The PAT shows what a PID in a PMT used in themultiplexed data indicates, and a PID of the PAT itself is registered aszero. The PMT stores PIDs of the streams of video, audio, subtitles andothers included in the multiplexed data, and attribute information ofthe streams corresponding to the PIDs. The PMT also has variousdescriptors relating to the multiplexed data. The descriptors haveinformation such as copy control information showing whether copying ofthe multiplexed data is permitted or not. The PCR stores STC timeinformation corresponding to an ATS showing when the PCR packet istransferred to a decoder, in order to achieve synchronization between anArrival Time Clock (ATC) that is a time axis of ATSs, and an System TimeClock (STC) that is a time axis of PTSs and DTSs.

FIG. 24 illustrates the data structure of the PMT in detail. A PMTheader is disposed at the top of the PMT. The PMT header describes thelength of data included in the PMT and others. A plurality ofdescriptors relating to the multiplexed data is disposed after the PMTheader. Information such as the copy control information is described inthe descriptors. After the descriptors, a plurality of pieces of streaminformation relating to the streams included in the multiplexed data isdisposed. Each piece of stream information includes stream descriptorseach describing information, such as a stream type for identifying acompression codec of a stream, a stream PID, and stream attributeinformation (such as a frame rate or an aspect ratio). The streamdescriptors are equal in number to the number of streams in themultiplexed data.

When the multiplexed data is recorded on a recording medium and others,it is recorded together with multiplexed data information files.

Each of the multiplexed data information files is management informationof the multiplexed data as shown in FIG. 25. The multiplexed datainformation files are in one to one correspondence with the multiplexeddata, and each of the files includes multiplexed data information,stream attribute information, and an entry map.

As illustrated in FIG. 25, the multiplexed data includes a system rate,a reproduction start time, and a reproduction end time. The system rateindicates the maximum transfer rate at which a system target decoder tobe described later transfers the multiplexed data to a PID filter. Theintervals of the ATSs included in the multiplexed data are set to nothigher than a system rate. The reproduction start time indicates a PTSin a video frame at the head of the multiplexed data. An interval of oneframe is added to a PTS in a video frame at the end of the multiplexeddata, and the PTS is set to the reproduction end time.

As shown in FIG. 26, a piece of attribute information is registered inthe stream attribute information, for each PID of each stream includedin the multiplexed data. Each piece of attribute information hasdifferent information depending on whether the corresponding stream is avideo stream, an audio stream, a presentation graphics stream, or aninteractive graphics stream. Each piece of video stream attributeinformation carries information including what kind of compression codecis used for compressing the video stream, and the resolution, aspectratio and frame rate of the pieces of picture data that is included inthe video stream. Each piece of audio stream attribute informationcarries information including what kind of compression codec is used forcompressing the audio stream, how many channels are included in theaudio stream, which language the audio stream supports, and how high thesampling frequency is. The video stream attribute information and theaudio stream attribute information are used for initialization of adecoder before the player plays back the information.

In Embodiment 7, the multiplexed data to be used is of a stream typeincluded in the PMT. Furthermore, when the multiplexed data is recordedon a recording medium, the video stream attribute information includedin the multiplexed data information is used. More specifically, themoving picture coding method or the moving picture coding apparatusdescribed in each of Embodiments includes a step or a unit forallocating unique information indicating video data generated by themoving picture coding method or the moving picture coding apparatus ineach of Embodiments, to the stream type included in the PMT or the videostream attribute information. With the configuration, the video datagenerated by the moving picture coding method or the moving picturecoding apparatus described in each of Embodiments can be distinguishedfrom video data that conforms to another standard.

Furthermore, FIG. 27 illustrates steps of the moving picture decodingmethod according to Embodiment 7. In Step exS100, the stream typeincluded in the PMT or the video stream attribute information isobtained from the multiplexed data. Next, in Step exS101, it isdetermined whether or not the stream type or the video stream attributeinformation indicates that the multiplexed data is generated by themoving picture coding method or the moving picture coding apparatus ineach of Embodiments. When it is determined that the stream type or thevideo stream attribute information indicates that the multiplexed datais generated by the moving picture coding method or the moving picturecoding apparatus in each of Embodiments, in Step exS102, the stream typeor the video stream attribute information is decoded by the movingpicture decoding method in each of Embodiments. Furthermore, when thestream type or the video stream attribute information indicatesconformance to the conventional standards, such as MPEG-2, MPEG-4 AVC,and VC-1, in Step exS103, the stream type or the video stream attributeinformation is decoded by a moving picture decoding method in conformitywith the conventional standards.

As such, allocating a new unique value to the stream type or the videostream attribute information enables determination whether or not themoving picture decoding method or the moving picture decoding apparatusthat is described in each of Embodiments can perform decoding. Even uponan input of multiplexed data that conforms to a different standard, anappropriate decoding method or apparatus can be selected. Thus, itbecomes possible to decode information without any error. Furthermore,the moving picture coding method or apparatus, or the moving picturedecoding method or apparatus in Embodiment 7 can be used in the devicesand systems described above.

Embodiment 8

Each of the moving picture coding method, the moving picture codingapparatus, the moving picture decoding method, and the moving picturedecoding apparatus in each of Embodiments is typically achieved in theform of an integrated circuit or a Large Scale Integrated (LSI) circuit.As an example of the LSI, FIG. 28 illustrates a configuration of the LSIex500 that is made into one chip. The LSI ex500 includes elements ex501,ex502, ex503, ex504, ex505, ex506, ex507, ex508, and ex509 to bedescribed below, and the elements are connected to each other through abus ex510. The power supply circuit unit ex505 is activated by supplyingeach of the elements with power when the power supply circuit unit ex505is turned on.

For example, when coding is performed, the LSI ex500 receives an AVsignal from a microphone ex117, a camera ex113, and others through an AVIO ex509 under control of a control unit ex501 including a CPU ex502, amemory controller ex503, a stream controller ex504, and a drivingfrequency control unit ex512. The received AV signal is temporarilystored in an external memory ex511, such as an SDRAM. Under control ofthe control unit ex501, the stored data is segmented into data portionsaccording to the computing amount and speed to be transmitted to asignal processing unit ex507. Then, the signal processing unit ex507codes an audio signal and/or a video signal. Here, the coding of thevideo signal is the coding described in each of Embodiments.Furthermore, the signal processing unit ex507 sometimes multiplexes thecoded audio data and the coded video data, and a stream IO ex506provides the multiplexed data outside. The provided multiplexed data istransmitted to the base station ex107, or written on the recording mediaex215. When data sets are multiplexed, the data sets should betemporarily stored in the buffer ex508 so that the data sets aresynchronized with each other.

Although the memory ex511 is an element outside the LSI ex500, it may beincluded in the LSI ex500. The buffer ex508 is not limited to onebuffer, but may be composed of buffers. Furthermore, the LSI ex500 maybe made into one chip or a plurality of chips.

Furthermore, although the control unit ex501 includes the CPU ex502, thememory controller ex503, the stream controller ex504, the drivingfrequency control unit ex512, the configuration of the control unitex501 is not limited to such. For example, the signal processing unitex507 may further include a CPU. Inclusion of another CPU in the signalprocessing unit ex507 can improve the processing speed. Furthermore, asanother example, the CPU ex502 may serve as or be a part of the signalprocessing unit ex507, and, for example, may include an audio signalprocessing unit. In such a case, the control unit ex501 includes thesignal processing unit ex507 or the CPU ex502 including a part of thesignal processing unit ex507.

The name used here is LSI, but it may also be called IC, system LSI,super LSI, or ultra LSI depending on the degree of integration.

Moreover, ways to achieve integration are not limited to the LSI, and aspecial circuit or a general purpose processor and so forth can alsoachieve the integration. Field Programmable Gate Array (FPGA) that canbe programmed after manufacturing LSIs or a reconfigurable processorthat allows re-configuration of the connection or configuration of anLSI can be used for the same purpose.

In the future, with advancement in semiconductor technology, a brand-newtechnology may replace LSI. The functional blocks can be integratedusing such a technology. The possibility is that the present inventionis applied to biotechnology.

Embodiment 9

When video data is decoded in the moving picture coding method or by themoving picture coding apparatus described in each of Embodiments,compared to when video data that conforms to a conventional standard,such as MPEG-2, MPEG-4 AVC, and VC-1, the computing amount probablyincreases. Thus, the LSI ex500 needs to be set to a driving frequencyhigher than that of the CPU ex502 to be used when video data inconformity with the conventional standard is decoded. However, when thedriving frequency is set higher, there is a problem that the powerconsumption increases.

In order to solve the problem, the moving picture decoding apparatus,such as the television ex300 and the LSI ex500 is configured todetermine to which standard the video data conforms, and switch betweenthe driving frequencies according to the determined standard. FIG. 29illustrates a configuration ex800 in Embodiment 9. A driving frequencyswitching unit ex803 sets a driving frequency to a higher drivingfrequency when video data is generated by the moving picture codingmethod or the moving picture coding apparatus described in each ofEmbodiments. Then, the driving frequency switching unit ex803 instructsa decoding processing unit ex801 that executes the moving picturedecoding method described in each of Embodiments to decode the videodata. When the video data conforms to the conventional standard, thedriving frequency switching unit ex803 sets a driving frequency to alower driving frequency than that of the video data generated by themoving picture coding method or the moving picture coding apparatusdescribed in each of Embodiments. Then, the driving frequency switchingunit ex803 instructs the decoding processing unit ex802 that conforms tothe conventional standard to decode the video data.

More specifically, the driving frequency switching unit ex803 includesthe CPU ex502 and the driving frequency control unit ex582 in FIG. 28.Here, each of the decoding processing unit ex802 that executes the videodecoding method described in each of Embodiments and the decodingprocessing unit ex802 that conforms to the conventional standardcorresponds to the signal processing unit ex507 in FIG. 28. The CPUex502 determines to which standard the video data conforms. Then, thedriving frequency control unit ex512 determines a driving frequencybased on a signal from the CPU ex502. Furthermore, the signal processingunit ex507 decodes the video data based on a signal from the CPU ex502.For example, the identification information described in Embodiment 7 isprobably used for identifying the video data. The identificationinformation is not limited to the one described in Embodiment 7 but maybe any information as long as the information indicates to whichstandard the video data conforms. For example, when which standard videodata conforms to can be determined based on an external signal fordetermining that the video data is used for a television or a disk,etc., the determination may be made based on such an external signal.Furthermore, the CPU ex502 selects a driving frequency based on, forexample, a look-up table in which the standards of the video data areassociated with the driving frequencies as shown in FIG. 31. The drivingfrequency can be selected by storing the look-up table in the bufferex508 and an internal memory of an LSI and with reference to the look-uptable by the CPU ex502.

FIG. 30 illustrates steps for executing a method in Embodiment 9. First,in Step exS200, the signal processing unit ex507 obtains identificationinformation from the multiplexed data. Next, in Step exS201, the CPUex502 determines whether or not the video data is generated based on theidentification information by the coding method and the coding apparatusdescribed in each of Embodiments. When the video data is generated bythe coding method and the coding apparatus described in each ofEmbodiments, in Step exS202, the CPU ex502 transmits a signal forsetting the driving frequency to a higher driving frequency to thedriving frequency control unit ex512. Then, the driving frequencycontrol unit ex512 sets the driving frequency to the higher drivingfrequency. On the other hand, when the identification informationindicates that the video data conforms to the conventional standard,such as MPEG-2, MPEG-4 AVC, and VC-1, in Step exS203, the CPU ex502transmits a signal for setting the driving frequency to a lower drivingfrequency to the driving frequency control unit ex512. Then, the drivingfrequency control unit ex512 sets the driving frequency to the lowerdriving frequency than that in the case where the video data isgenerated by the coding method and the coding apparatus described ineach of Embodiment.

Furthermore, along with the switching of the driving frequencies, thepower conservation effect can be improved by changing the voltage to beapplied to the LSI ex500 or an apparatus including the LSI ex500. Forexample, when the driving frequency is set lower, the voltage to beapplied to the LSI ex500 or the apparatus including the LSI ex500 isprobably set to a voltage lower than that in the case where the drivingfrequency is set higher.

Furthermore, when the computing amount for decoding is larger, thedriving frequency may be set higher, and when the computing amount fordecoding is smaller, the driving frequency may be set lower as themethod for setting the driving frequency. Thus, the setting method isnot limited to the ones described above. For example, when the computingamount for decoding video data in conformity with MPEG-4 AVC is largerthan the computing amount for decoding video data generated by themoving picture coding method and the moving picture coding apparatusdescribed in each of Embodiments, the driving frequency is probably setin reverse order to the setting described above.

Furthermore, the method for setting the driving frequency is not limitedto the method for setting the driving frequency lower. For example, whenthe identification information indicates that the video data isgenerated by the moving picture coding method and the moving picturecoding apparatus described in each of Embodiments, the voltage to beapplied to the LSI ex500 or the apparatus including the LSI ex500 isprobably set higher. When the identification information indicates thatthe video data conforms to the conventional standard, such as MPEG-2,MPEG-4 AVC, and VC-1, the voltage to be applied to the LSI ex500 or theapparatus including the LSI ex500 is probably set lower. As anotherexample, when the identification information indicates that the videodata is generated by the moving picture coding method and the movingpicture coding apparatus described in each of Embodiments, the drivingof the CPU ex502 does not probably have to be suspended. When theidentification information indicates that the video data conforms to theconventional standard, such as MPEG-2, MPEG-4 AVC, and VC-1, the drivingof the CPU ex502 is probably suspended at a given time because the CPUex502 has extra processing capacity. Even when the identificationinformation indicates that the video data is generated by the movingpicture coding method and the moving picture coding apparatus describedin each of Embodiments, in the case where the CPU ex502 may have a timedelay, the driving of the CPU ex502 is probably suspended at a giventime. In such a case, the suspending time is probably set shorter thanthat in the case where when the identification information indicatesthat the video data conforms to the conventional standard, such asMPEG-2, MPEG-4 AVC, and VC-1.

Accordingly, the power conservation effect can be improved by switchingbetween the driving frequencies in accordance with the standard to whichthe video data conforms. Furthermore, when the LSI ex500 or theapparatus including the LSI ex500 is driven using a battery, the batterylife can be extended with the power conservation effect.

Embodiment 10

There are cases where a plurality of video data that conforms to adifferent standard, is provided to the devices and systems, such as atelevision and a mobile phone. In order to enable decoding the pluralityof video data that conforms to the different standards, the signalprocessing unit ex507 of the LSI ex500 needs to conform to the differentstandards. However, the problems of increase in the scale of the circuitof the LSI ex500 and increase in the cost arise with the individual useof the signal processing units ex507 that conform to the respectivestandards.

In order to solve the problem, what is conceived is a configuration inwhich the decoding processing unit for implementing the moving picturedecoding method described in each of Embodiments and the decodingprocessing unit that conforms to the conventional standard, such asMPEG-2, MPEG-4 AVC, and VC-1 are partly shared. Ex900 in FIG. 32A showsan example of the configuration. For example, the moving picturedecoding method described in each of Embodiments and the moving picturedecoding method that conforms to MPEG-4 AVC have, partly in common, thedetails of processing, such as entropy coding, inverse quantization,deblocking filtering, and motion compensated prediction. The details ofprocessing to be shared probably include use of a decoding processingunit ex902 that conforms to MPEG-4 AVC. In contrast, a dedicateddecoding processing unit ex901 is probably used for other processingunique to the present invention. Since the present invention ischaracterized by motion compensation in particular, for example, thededicated decoding processing unit ex901 is used for the motioncompensation. Otherwise, the decoding processing unit is probably sharedfor one of the entropy coding, inverse quantization, deblockingfiltering, and inverse quantization, or all of the processing. Thedecoding processing unit for implementing the moving picture decodingmethod described in each of Embodiments may be shared for the processingto be shared, and a dedicated decoding processing unit may be used forprocessing unique to that of MPEG-4 AVC.

Furthermore, ex1000 in FIG. 32B shows another example in that processingis partly shared. This example uses a configuration including adedicated decoding processing unit ex1001 that supports the processingunique to the present invention, a dedicated decoding processing unitex1002 that supports the processing unique to another conventionalstandard, and a decoding processing unit ex1003 that supports processingto be shared between the moving picture decoding method in the presentinvention and the conventional moving picture decoding method. Here, thededicated decoding processing units ex1001 and ex1002 are notnecessarily specialized for the processing of the present invention andthe processing of the conventional standard, respectively, and may bethe ones capable of implementing general processing. Furthermore, theconfiguration of Embodiment 10 can be implemented by the LSI ex500.

As such, reducing the scale of the circuit of an LSI and reducing thecost are possible by sharing the decoding processing unit for theprocessing to be shared between the moving picture decoding method inthe present invention and the moving picture decoding method inconformity with the conventional standard.

INDUSTRIAL APPLICABILITY

The image coding method and the image decoding method according to thepresent invention are applicable to, for example, televisions, digitalvideo recorders, car navigation systems, cellular phones, digitalcameras, and digital video cameras.

1. An image coding method of coding a current picture per block withprediction using one or both of a first reference picture list and asecond reference picture list, said method comprising: adding, to acandidate list, a first adjacent motion vector as a candidate for apredicted motion vector to be used for coding a current motion vector,the first adjacent motion vector being a motion vector of a blockadjacent to a current block included in the current picture, and thecurrent motion vector being a motion vector of the current block;selecting the predicted motion vector to be used for coding the currentmotion vector, from the candidate list including the first adjacentmotion vector; and coding the current motion vector using the selectedpredicted motion vector, wherein in said adding, the first adjacentmotion vector is added to the candidate list for the current motionvector, the first adjacent motion vector indicating a position in afirst reference picture included in the first reference picture list,and the current motion vector indicating a position in a secondreference picture included in the second reference picture list.
 2. Theimage coding method according to claim 1, wherein in said adding, asecond adjacent motion vector is further added, the second adjacentmotion vector being a motion vector of the adjacent block and indicatinga position in a third reference picture included in the second referencepicture list.
 3. The image coding method according to claim 2, whereinin said adding: it is determined whether or not the second referencepicture is identical to the third reference picture; the second adjacentmotion vector is added to the candidate list when it is determined thatthe second reference picture is identical to the third referencepicture; it is determined whether or not the second reference picture isidentical to the first reference picture; and the first adjacent motionvector is added to the candidate list when it is determined that thesecond reference picture is identical to the first reference picture. 4.The image coding method according to claim 3, wherein in said adding: itis determined whether or not the second reference picture is identicalto the first reference picture when it is determined that the secondreference picture is not identical to the third reference picture; andthe first adjacent motion vector is added to the candidate list when itis determined that the second reference picture is not identical to thethird reference picture and that the second reference picture isidentical to the first reference picture.
 5. The image coding methodaccording to claim 3, wherein in said adding: it is determined whetheror not the second reference picture is identical to the third referencepicture by determining whether or not a display order of the secondreference picture identified by the second reference picture list and asecond reference index is identical to a display order of the thirdreference picture identified by the second reference picture list and athird reference index; and it is determined whether or not the secondreference picture is identical to the first reference picture bydetermining whether or not the display order of the second referencepicture identified by the second reference picture list and the secondreference index is identical to a display order of the first referencepicture identified by the first reference picture list and a firstreference index.
 6. The image coding method according to claim 3,wherein in said adding, a motion vector having a magnitude of 0 is addedas the candidate for the predicted motion vector, when it is determinedthat the second reference picture is not identical to the thirdreference picture and that the second reference picture is not identicalto the first reference picture.
 7. The image coding method according toclaim 1, wherein in said adding, a plurality of index values and aplurality of candidates for the predicted motion vector are added to thecandidate list so that the index values are in one-to-one correspondencewith the candidates for the predicted motion vector, in said selecting,an index value is selected from the candidate list as the predictedmotion vector, and in said coding, the selected index value is coded sothat a code of the index value is longer as the index value is larger.8. The image coding method according to claim 1, wherein in said adding,the first adjacent motion vector of the adjacent block is added to thecandidate list, the adjacent block being one of a left adjacent block,an above-adjacent block, and an upper right adjacent block with respectto the current block.
 9. An image decoding method of decoding a currentpicture per block with prediction using one or both of a first referencepicture list and a second reference picture list, said methodcomprising: adding, to a candidate list, a first adjacent motion vectoras a candidate for a predicted motion vector to be used for decoding acurrent motion vector, the first adjacent motion vector being a motionvector of a block adjacent to a current block included in the currentpicture, and the current motion vector being a motion vector of thecurrent block; selecting the predicted motion vector to be used fordecoding the current motion vector, from the candidate list includingthe first adjacent motion vector; and decoding the current motion vectorusing the selected predicted motion vector, wherein in said adding, thefirst adjacent motion vector is added to the candidate list for thecurrent motion vector, the first adjacent motion vector indicating aposition in a first reference picture included in the first referencepicture list, and the current motion vector indicating a position in asecond reference picture included in the second reference picture list.10. The image decoding method according to claim 9, wherein in saidadding, a second adjacent motion vector is further added, the secondadjacent motion vector being a motion vector of the adjacent block andindicating a position in a third reference picture included in thesecond reference picture list.
 11. The image decoding method accordingto claim 10, wherein in said adding: it is determined whether or not thesecond reference picture is identical to the third reference picture;the second adjacent motion vector is added to the candidate list when itis determined that the second reference picture is identical to thethird reference picture; it is determined whether or not the secondreference picture is identical to the first reference picture; and thefirst adjacent motion vector is added to the candidate list when it isdetermined that the second reference picture is identical to the firstreference picture.
 12. The image decoding method according to claim 11,wherein in said adding: it is determined whether or not the secondreference picture is identical to the first reference picture when it isdetermined that the second reference picture is not identical to thethird reference picture; and the first adjacent motion vector is addedto the candidate list when it is determined that the second referencepicture is not identical to the third reference picture and that thesecond reference picture is identical to the first reference picture.13. The image decoding method according to claim 11, wherein in saidadding: it is determined whether or not the second reference picture isidentical to the third reference picture by determining whether or not adisplay order of the second reference picture identified by the secondreference picture list and a second reference index is identical to adisplay order of the third reference picture identified by the secondreference picture list and a third reference index; and it is determinedwhether or not the second reference picture is identical to the firstreference picture by determining whether or not the display order of thesecond reference picture identified by the second reference picture listand the second reference index is identical to a display order of thefirst reference picture identified by the first reference picture listand a first reference index.
 14. The image decoding method according toclaim 11, wherein in said adding, a motion vector having a magnitude of0 is added as the candidate for the predicted motion vector, when it isdetermined that the second reference picture is not identical to thethird reference picture and that the second reference picture is notidentical to the first reference picture.
 15. The image decoding methodaccording to claim 9, wherein in said adding, a plurality of indexvalues and a plurality of candidates for the predicted motion vector areadded to the candidate list so that the index values are in one-to-onecorrespondence with the candidates for the predicted motion vector, insaid decoding, an index value is decoded, the index value being coded sothat a code of the index value is longer as the index value is larger,and in said selecting, the predicted motion vector corresponding to thedecoded index value is selected from the candidate list.
 16. The imagedecoding method according to claim 9, wherein in said adding, the firstadjacent motion vector of the adjacent block is added to the candidatelist, the adjacent block being one of a left adjacent block, anabove-adjacent block, and an upper right adjacent block with respect tothe current block.
 17. An image coding apparatus that codes a currentpicture per block with prediction using one or both of a first referencepicture list and a second reference picture list, said apparatuscomprising: an addition unit configured to add, to a candidate list, afirst adjacent motion vector as a candidate for a predicted motionvector to be used for coding a current motion vector, the first adjacentmotion vector being a motion vector of a block adjacent to a currentblock included in the current picture, and the current motion vectorbeing a motion vector of the current block; a selecting unit configuredto select the predicted motion vector to be used for coding the currentmotion vector, from the candidate list including the first adjacentmotion vector; and a coding unit configured to code the current motionvector using the selected predicted motion vector, wherein said additionunit is configured to add the first adjacent motion vector to thecandidate list for the current motion vector, the first adjacent motionvector indicating a position in a first reference picture included inthe first reference picture list, and the current motion vectorindicating a position in a second reference picture included in thesecond reference picture list.
 18. An image decoding apparatus thatdecodes a current picture per block with prediction using one or both ofa first reference picture list and a second reference picture list, saidapparatus comprising: an addition unit configured to add, to a candidatelist, a first adjacent motion vector as a candidate for a predictedmotion vector to be used for decoding a current motion vector, the firstadjacent motion vector being a motion vector of a block adjacent to acurrent block included in the current picture, and the current motionvector being a motion vector of the current block; a selecting unitconfigured to select the predicted motion vector to be used for decodingthe current motion vector, from the candidate list including the firstadjacent motion vector; and a decoding unit configured to decode thecurrent motion vector using the selected predicted motion vector,wherein said addition unit is configured to add the first adjacentmotion vector to the candidate list for the current motion vector, thefirst adjacent motion vector indicating a position in a first referencepicture included in the first reference picture list, and the currentmotion vector indicating a position in a second reference pictureincluded in the second reference picture list.
 19. An image coding anddecoding apparatus that codes a current picture per block and decodes acurrent picture per block, with prediction using one or both of a firstreference picture list and a second reference picture list, saidapparatus comprising: an addition unit configured to add, to a candidatelist, a first adjacent motion vector as a candidate for a predictedmotion vector to be used for coding or decoding a current motion vector,the first adjacent motion vector being a motion vector of a blockadjacent to a current block to be processed and included in the currentpicture to be coded or decoded, and the current motion vector being amotion vector of the current block; a selecting unit configured toselect the predicted motion vector to be used for coding or decoding thecurrent motion vector, from the candidate list including the firstadjacent motion vector; a coding unit configured to code the currentmotion vector using the selected predicted motion vector; and a decodingunit configured to decode the current motion vector using the selectedpredicted motion vector, wherein said addition unit is configured to addthe first adjacent motion vector to the candidate list for the currentmotion vector, the first adjacent motion vector indicating a position ina first reference picture included in the first reference picture list,and the current motion vector indicating a position in a secondreference picture included in the second reference picture list.